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Wednesday, February 16, 2011

Cardiac surgery

Two cardiac surgeons performing a cardiac surgery known as coronary
artery bypass surgery. Note the use of a steel retractor used
 to forcefully maintain the exposure of the patient's heart.
Cardiovascular surgery is a surgery on the heart and/or great vessels performed by cardiac surgeons. Frequently, it is done to treat complications of ischemic heart disease (for example, coronary artery bypass grafting), correct congenital heart disease, or treat valvular heart disease caused by various causes including endocarditis. It also includes heart transplantation.


The earliest operations on the pericardium (the sac that surrounds the heart) took place in the 19th century and were performed by, Francisco Romero Dominique Jean Larrey, Henry Dalton, and Daniel Hale Williams. The first surgery on the heart itself was performed by Norwegian surgeon Axel Cappelen on the 4th of September 1895 at Rikshospitalet in Kristiania, now Oslo. He ligated a bleeding coronary artery in a 24 year old man who had been stabbed in the left axillae and was in deep shock upon arrival. Access was through a left thoracotomy. The patient awoke and seemed fine for 24hrs, but became ill with increasing temperature and he ultimately died from what the post mortem proved to be mediastinitis on the 3rd postoperative day. The first successful surgery of the heart, performed without any complications, was by Dr. Ludwig Rehn of Frankfurt, Germany, who repaired a stab wound to the right ventricle on September 7, 1896.
Surgery in great vessels (aortic coarctation repair, Blalock-Taussig shunt creation, closure of patent ductus arteriosus), became common after the turn of the century and falls in the domain of cardiac surgery, but technically cannot be considered heart surgery.

Heart Malformations – Early Approaches
In 1925 operations on the valves of the heart were unknown. Henry Souttar operated successfully on a young woman with mitral stenosis. He made an opening in the appendage of the left atrium and inserted a finger into this chamber in order to palpate and explore the damaged mitral valve. The patient survived for several years but Souttar’s physician colleagues at that time decided the procedure was not justified and he could not continue.
Cardiac surgery changed significantly after World War II. In 1948 four surgeons carried out successful operations for mitral stenosis resulting from rheumatic fever. Horace Smithy (1914–1948) of Charlotte, revived an operation due to Dr Dwight Harken of the Peter Bent Brigham Hospital using a punch to remove a portion of the mitral valve. Charles Bailey (1910–1993) at the Hahnemann Hospital, Philadelphia, Dwight Harken in Boston and Russell Brock at Guy’s Hospital all adopted Souttar’s method. All these men started work independently of each other, within a few months. This time Souttar’s technique was widely adopted although there were modifications.
In 1947 Thomas Holmes Sellors (1902–1987) of the Middlesex Hospital operated on a Fallot’s Tetralogy patient with pulmonary stenosis and successfully divided the stenosed pulmonary valve. In 1948, Russell Brock, probably unaware of Sellor’s work, used a specially designed dilator in three cases of pulmonary stenosis. Later in 1948 he designed a punch to resect the infundibular muscle stenosis which is often associated with Fallot’s Tetralogy. Many thousands of these “blind” operations were performed until the introduction of heart bypass made direct surgery on valves possible.
[edit]Open heart surgery
This is a surgery in which the patient's heart is opened and surgery is performed on the internal structures of the heart.
It was soon discovered by Dr. Wilfred G. Bigelow of the University of Toronto that the repair of intracardiac pathologies was better done with a bloodless and motionless environment, which means that the heart should be stopped and drained of blood. The first successful intracardiac correction of a congenital heart defect using hypothermia was performed by Dr. C. Walton Lillehei and Dr. F. John Lewis at the University of Minnesota on September 2, 1952. The following year, Soviet surgeon Aleksandr Aleksandrovich Vishnevskiy conducted the first cardiac surgery under local anesthesia.
Surgeons realized the limitations of hypothermia – complex intracardiac repairs take more time and the patient needs blood flow to the body (and particularly the brain); the patient needs the function of the heart and lungs provided by an artificial method, hence the term cardiopulmonary bypass. Dr. John Heysham Gibbon at Jefferson Medical School in Philadelphia reported in 1953 the first successful use of extracorporeal circulation by means of an oxygenator, but he abandoned the method, disappointed by subsequent failures. In 1954 Dr. Lillehei realized a successful series of operations with the controlled cross-circulation technique in which the patient's mother or father was used as a 'heart-lung machine'. Dr. John W. Kirklin at the Mayo Clinic in Rochester, Minnesota started using a Gibbon type pump-oxygenator in a series of successful operations, and was soon followed by surgeons in various parts of the world.
Dr. Nazih Zuhdi worked for four years under Drs. Clarence Dennis, Karl Karlson, and Charles Fries, who built an early pump-oxygenator. Zuhdi and Fries worked on several designs and re-designs of Dennis' earlier model from 1952–1956 at the Brooklyn Center. Zuhdi then went to work with Dr. C. Walton Lillehei at the University of Minnesota. Lillehei had designed his own version of a cross-circulation machine, which came to become known as the DeWall-Lillehei heart-lung machine. Zuhdi worked on perfusion and blood flow trying to solve the problem of air bubbles while bypassing the heart so the heart could be stopped for the operation. Zuhdi moved to Oklahoma City, OK, in 1957, and began working at the Oklahoma University College. Zuhdi, the heart surgeon, teamed up with Dr. Allen Greer, a lung surgeon and Dr. John Carey, forming a three man open heart surgery team. With the advent of Dr. Zuhdi's heart-lung machine which was modified in size, being much smaller than the DeWall-Lillehei heart-lung machine, and with other modifications, reduced the need for blood down to a minimal amount, and the cost of the equipment down to $500.00 and also reduced the prep time from two hours to 20 minutes. Dr. Zuhdi performed the first Total Intentional Hemodilution open heart surgery on Terry Gene Nix, age 7, on February 25, 1960, at Mercy Hospital, Oklahoma City, OK. The operation was a success; however, Nix died three years later in 1963. In March, 1961, Zuhdi, Carey, and Greer, performed open heart surgery on a child, age 3½, using the Total Intentional Hemodilution machine, with success. That patient is still alive.
In 1985 Dr. Zuhdi performed Oklahoma's first successful heart transplant on Nancy Rogers at Baptist Hospital. The transplant was successful, but Rogers, a cancer sufferer, died from an infection 54 days after surgery.

Modern beating-heart surgery
Since the 1990s, surgeons have begun to perform "off-pump bypass surgery" – coronary artery bypass surgery without the aforementioned cardiopulmonary bypass. In these operations, the heart is beating during surgery, but is stabilized to provide an almost still work area. Some researchers believe this approach results in fewer post-operative complications (such as postperfusion syndrome) and better overall results (study results are controversial as of 2007, the surgeon's preference and hospital results still play a major role).

Minimally invasive surgery
A new form of heart surgery that has grown in popularity is robot-assisted heart surgery. This is where a machine is used to perform surgery while being controlled by the heart surgeon. The main advantage to this is the size of the incision made in the patient. Instead of an incision being at least big enough for the surgeon to put his hands inside, it does not have to be bigger than 3 small holes for the robot's much smaller hands to get through.

Pediatric Cardiovascular Surgery
Pediatric Cardiovascular Surgery is surgery of the heart of children. Russell M. Nelson performed the first successful pediatric cardiac operation at the Salt Lake General Hospital in March 1956, a total repair of tetralogy of Fallot in a four-year-old girl.


The development of cardiac surgery and cardiopulmonary bypass techniques has reduced the mortality rates of these surgeries to relatively low ranks. For instance, repairs of congenital heart defects are currently estimated to have 4–6% mortality rates.
A major concern with cardiac surgery is the incidence of neurological damage. Stroke occurs in 2–3% of all people undergoing cardiac surgery, and is higher in patients at risk for stroke.A more subtle constellation of neurocognitive deficits attributed to cardiopulmonary bypass is known as postperfusion syndrome (sometimes called 'pumphead'). The symptoms of postperfusion syndrome were initially felt to be permanent,but were shown to be transient with no permanent neurological impairment.

See also

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Open Heart Surgery

Open Heart Surgery
Studio album by Virginwool
ReleasedAugust 8, 2000
ProducerBrad Wood
Open Heart Surgery was released on August 8, 2000 by rock band Virginwool. The band signed to Breaking/Atlantic Records after initially beginning signed to Universal Records. The album was produced and mixed by Brad Wood.
"I Think Her Mother Loves Me" was the first single from the album. A remixed, slightly poppier version was released. "Better for You" was the second single, and it too was released in a shorter radio edit. The tracks "You're the Girl" and "Picked Apart" were previously released on the band's self-released CDs while they were still known as Gumwrapper Curb. "Picked Apart" was originally entitled "Virgin Wool".
The album is now out of print.

Track listing

"Nevermind Her Hips"
"I Think Her Mother Loves Me"
"You're the Girl"
"Climbing Boulders"
"Better for You"
"Lonely Man"
"Goodman Vibe"
"Picked Apart"
"New Song"
"Between the Lies"

Jordan Pouzzner – vocals
Gar Willard – guitars
Adam Loewy – bass
Brett Crook – drums, percussion


Climate of the United States

Climate zones of the Continental United States.
The United States includes a wide variety of climate types due to its large size, range of geographic features, and non-contiguous arrangement. In the contiguous United States to the east of the 100th meridian, the climate ranges from humid continental in the north to humid subtropical in the south. The southern tip of Florida is tropical. The Great Plains west of the 100th meridian are semi-arid. Much of the Rocky Mountains, the Sierra Nevada, and the Cascade Range are alpine. The climate is arid in the Great Basin, desert in the Southwest, Mediterranean in coastal California, and oceanic in coastal Oregon and Washington. The state of Alaska—on the northwestern corner of the North American continent—is largely subarctic, with an oceanic climate in its southern edge and a polar climate in the north. The archipelago state of Hawaii, in the middle of the Pacific Ocean, is tropical.
Extreme weather is not uncommon—the states bordering the Gulf of Mexico are prone to hurricanes, and tornadoes regularly occur in the area of the Midwest referred to as Tornado Alley. The United States has more tornadoes than the rest of the countries of the world combined.

Deep snow during the Blizzard of 2006 Nor'easter in Brooklyn, New York City.
The main influence on weather in the United States is the polar jet stream, which brings in large low pressure systems from the northern Pacific Ocean. Once a Pacific cyclone moves over the Great Plains, uninterrupted flat land allows it to reorganize and can lead to major clashes of air masses. Sometimes during late winter and spring these storms can combine with another low pressure system as they move up the East Coast and into the Atlantic Ocean, where they intensify rapidly. These storms are known as Nor'easters and often bring widespread, heavy snowfall to the Mid-Atlantic and New England. The uninterrupted flat grasslands of the Great Plains also leads to some of the most extreme climate swings in the world. Temperatures can rise or drop rapidly; winds can be extreme; and the flow of heat waves or Arctic air masses often advance uninterrupted through the plains.
The Great Basin and Columbia Plateau (the Intermontane Plateaus) are arid or semiarid regions that lie in the rain shadow of the Cascades and Sierra Nevada. Precipitation averages less than 15 inches (38 cm). The Southwest is a hot desert, with temperatures exceeding 100°F (38°C) for several weeks at a time in summer. The Southwest and the Great Basin are also affected by the monsoon from the Gulf of California from July-September, which brings localized but often severe thunderstorms to the region.


Average precipitation.

The characteristics of rainfall across the United States differ significantly across the United States and its possessions. Late summer and fall extratropical cyclones bring a majority of the precipitation which falls across western, southern, and southeast Alaska annually. During the fall, winter, and spring, Pacific storm systems bring most of Hawaii and the western United States much of their precipitation. Nor'easters moving up the East coast bring cold season precipitation to the Mid-Atlantic and New England states. Lake-effect snows add to precipitation potential downwind of the Great Lakes, as well as Great Salt Lake and the Finger Lakes during the cold season. The snow to liquid ratio across the contiguous United States is 13:1, meaning 13 inches (330 mm) of snow melts down to 1 inch (25 mm) of water.The El Niño-Southern Oscillation affects the precipitation distribution, by altering rainfall patterns across the West, Midwest, the Southeast, and throughout the tropics.
During the summer, the Southwest monsoon combined with Gulf of California and Gulf of Mexico moisture moving around the subtropical ridge in the Atlantic ocean bring the promise of afternoon and evening thunderstorms to the southern tier of the country as well as the Great Plains.Equatorward of the subtropical ridge, tropical cyclones enhance precipitation across southern and eastern sections of the country, as well as Puerto Rico, the United States Virgin Islands, the Northern Mariana Islands, Guam, and American Samoa. Over the top of the ridge, the jet stream brings a summer precipiation maximum to the Great Lakes. Large thunderstorm areas known as mesoscale convective complexes move through the Plains, Midwest, and Great Lakes during the warm season, contributing up to 10% of the annual precipitation to the region.


Several different air masses affect the United States.
In northern Alaska, tundra and arctic conditions predominate, and the temperature has fallen as low as −80 °F (−62 °C). On the other end of the spectrum, Death Valley, California once reached 134 °F (56.7 °C), the second-highest temperature ever recorded on Earth.

On average, the mountains of the western states receive the highest levels of snowfall on Earth. The greatest annual snowfall level is at Mount Rainier in Washington, at 692 inches (1,758 cm); the record there was 1,122 inches (2,850 cm) in the winter of 1971–72. This record was broken by the Mt. Baker Ski Area in northwestern Washington which reported 1,140 inches (2,896 cm) of snowfall for the 1998-99 snowfall season. Other places with significant snowfall outside the Cascade Range are the Wasatch Mountains, near the Great Salt Lake and the Sierra Nevada, near Lake Tahoe.
Along the coastal mountain ranges in the Pacific Northwest, rainfall is greater than anywhere else in the continental U.S., with Quinault Ranger in Washington having an average of 137 inches (3,480 mm). Hawaii receives even more, with 460 inches (11,684 mm) measured annually, on average, on Mount Waialeale, in Kauai. The Mojave Desert in the southwest is home to the driest locale in the U.S. Yuma, Arizona, has an average of 2.63 inches (67 mm) of precipitation each year.

[hide]Climate data for United States
Record high °F (°C)98
Record low °F (°C)−80
Source: http://www.infoplease.com/ipa/A0762182.html

Natural disasters

 Floods in the United States,United States hurricanes, and Tornadoes in the United States
Total devastation in Gulfport, Mississippi following Hurricane Katrina in 2005.
The United States is affected by a large variety of weather related natural disasters. Deadly and destructive hurricanes occur almost every year along the Atlantic seaboard and the Gulf of Mexico. Hurricanes can also strike Hawaii in the Pacific Ocean. Particularly at risk are the central and southern Texas coasts, the area from southeastern Louisiana east to the Florida Panhandle, the east coast of Florida, and the Outer Banks of North Carolina. Hurricane season runs from June 1 to November 30, with a peak from mid-August through early October. Some of the more devastating hurricanes have included the Galveston Hurricane of 1900, Hurricane Andrew in 1992, and Hurricane Katrina in 2005. The remnants of tropical cyclones from the Eastern Pacific also occasionally impact the southwestern United States, bringing sometimes heavy rainfall.

A powerful tornado in Texas.
The Great Plains and Midwest, because of the contrasting air masses, have frequent severe thunderstorms and tornado outbreaks during spring and summer. In central portions of the U.S., tornadoes are more common than anywhere else on Earth and touch down most commonly in the spring and summer. The strip of land from north Texas north to Nebraska and east into Southern Michigan is known as Tornado Alley, where many houses have tornado shelters and many towns have tornado sirens.

The Appalachian region and the Midwest experience the worst floods. Widespread severe flooding is rare. Some exceptions include the Great Mississippi Flood of 1927, the Great Flood of 1993, and widespread flooding and mudslides caused by the 1982-1983 El Niño event in the western United States. Localized flooding can, however, occur anywhere, and mudslides from heavy rain can cause problems in any mountainous area, particularly the Southwest. The narrow canyons of many mountain areas in the west and severe thunderstorm activity during the monsoon season in summer leads to sometimes devastating flash floods as well, while Nor'easter snowstorms can bring activity to a halt throughout the Northeast (although heavy snowstorms can occur almost anywhere).
The Southwest has the worst droughts; one is thought to have lasted over 500 years and to have decimated the Anasazi people. Large stretches of desert shrub in the west can fuel the spread of wildfires. Although severe drought is rare, it has occasionally caused major problems, such as during the Dust Bowl (1931–1942), which coincided with the Great Depression. Farmland failed throughout the Plains, entire regions were virtually depopulated, and dust storms ravaged the land. More recently, the western U.S. experienced widespread drought from 1999-2004.

Hurricanes - Sunspot theory

A 2010 report correlates low sunspot activity with high hurricane activity. Analyzing historical data, there was a 25% chance of at least one hurricane striking the continental US during a peak sunspot year; a 64% chance during a low sunspot year. In June 2010, the hurricanes predictors in the US were not using this information.

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Climate of Minnesota

On March 29, 1881 snowdrifts in Minnesota
were higher than locomotives.
The climate of Minnesota is typical of a continental climate, with cold winters and hot summers. The state's location in the Upper Midwest allows it to experience some of the widest variety of weather in the United States, with each of the four seasons having its own distinct characteristics. The areas near Lake Superior in the Minnesota Arrowhead region experience weather unique from the rest of the state. The moderating effect of Lake Superior keeps the surrounding area relatively cooler in the summer and relatively warmer in the winter, giving that region more of a maritime climate. On the Köppen climate classification, the southern third of Minnesota—roughly from the Twin Cities region southward—falls in the hot summer humid continental climate zone (Dfa), and the northern two-thirds of Minnesota falls in the warm summer humid continental climate zone (Dfb).
Winter in Minnesota is characterized by cold (below freezing) temperatures. Snow is the main form of winter precipitation, but freezing rain, ice, sleet, and occasionally rain are all possible during the winter months. Common storm systems include Alberta clippers or Panhandle hooks; some of which evolve into blizzards. Annual snowfall extremes have ranged from over 170 inches (432 cm) in the rugged Superior Highlands of the North Shore to as little as 10 inches (25 cm) in southern Minnesota. Temperatures as low as −60 °F (−51 °C) have occurred during Minnesota winters. Spring is a time of major transition in Minnesota. Snowstorms are common early in the spring, but by late-spring as temperatures begin to moderate the state can experience tornado outbreaks, a risk which diminishes but does not cease through the summer and into the fall.
In summer, heat and humidity predominate in the south, while warm and less humid conditions are generally present in the north. These humid conditions help kick off thunderstorm activity 30–40 days per year. Summer high temperatures in Minnesota average in the mid-80s F (30 °C) in the south to the upper-70s F (25 °C) in the north, with temperatures as hot as 114 °F (46 °C) possible. The growing season in Minnesota varies from 90 days per year in the Iron Range to 160 days in southeast Minnesota. Tornadoes are possible in Minnesota from March through November, but the peak tornado month is June, followed by July, May, and August. The state averages 24 tornadoes per year. Minnesota is the driest state in the Midwest. Average annual precipitation across the state ranges from around 35 inches (890 mm) in the southeast to 20 inches (510 mm) in the northwest. Autumn weather in Minnesota is largely the reverse of spring weather. The jet stream—which tends to weaken in summer—begins to re-strengthen, leading to a quicker changing of weather patterns and an increased variability of temperatures. By late October and November these storm systems become strong enough to form major winter storms. Fall and spring are the windiest times of the year in Minnesota.

General climatology
The average daily temperature of Minneapolis, Minnesota
varies from 13 °F (−11 °C) to 73 °F (23 °C).
Because of its location in the center of North America, Minnesota experiences temperature extremes characteristic of a continental climate, with cold winters and mild to hot summers in the south and frigid winters and generally cool summers in the north. Each season has distinctive upper air patterns which bring different weather conditions with them. Being 1,000 miles (1,609 km) from any large body of water (with the exception of Lake Superior), Minnesota receives temperatures and precipitation that vary widely. It is far enough north to experience −60 °F (−51 °C) temperatures and blizzards during the winter months, but far enough south to experience 114 °F (46 °C) temperatures and tornado outbreaks in the summer. The 174 degree Fahrenheit (97 °C) variation between Minnesota's highest and lowest temperature is the 11th largest variation of any U.S. state, and 3rd largest of any non-mountainous state (behind North Dakota and South Dakota).
Minnesota is far from major sources of moisture and is in the transition zone between the moist East and the arid Great Plains. Annual average precipitation across the state ranges from around 35 inches (890 mm) in the southeast to 20 inches (510 mm) in the northwest. Snow is the main form of precipitation from November through March, while rain is the most common the rest of the year. Annual snowfall extremes have ranged from over 170 inches (432 cm) in the rugged Superior Highlands of the North Shore to as little as 2.3 inches (5.8 cm) in southern Minnesota. It has snowed in Minnesota during every month with the exception of July, and the state averages 110 days per year with snow cover of an inch (2.5 cm) or greater.

Lake Superior
The cool, moist air near Lake Superior makes
 fog a frequent occurrence near the shore.
Lake Superior moderates the climate of those parts of Minnesota's Arrowhead Region near the shore. The lake acts as a heat sink, keeping the state's North Shore area relatively cooler in the summer and warmer in the winter. While this effect is marked near the lake, it does not reach very far inland. For example, Grand Marais on the lakeshore has an average July high temperature of 70 °F (21 °C), while Virginia, at about the same latitude but inland about 100 miles (161 km) to the west, has an average July high of 77 °F (25 °C). Conversely, Virginia's average high temperature in January is 15 °F (−9 °C), while Grand Marais' is 23 °F (−5 °C). Just a few miles inland from Lake Superior are the Sawtooth Mountains, which almost completely confine the marine air masses and associated precipitation to lower elevations near the lake.
The prevailing northwest winter winds also limit the lake's influence. Places near the shoreline can receive lake-effect snow, but because the state lies north and west of the lake, snowfall amounts are not nearly as large as they are in locations like Wisconsin and Michigan that lie downwind to the south. Even so, the single largest snowstorm in Minnesota history was a lake effect event. On January 6, 1994 Finland, Minnesota, received 36 inches (91 cm) of lake effect snow in 24 hours, and 47 inches (119 cm) over a three day period. Both are Minnesota records. At 85 inches (216 cm) per year, the port city of Duluth has the highest average snowfall total of any city in Minnesota. At 58.9 °F (14.9 °C), Grand Marais has the lowest average summer temperature of any city in the state.
The climatological effects of Lake Superior tend to stifle convection, thus limiting the potential for tornadoes. Although Cook and Lake counties are two of the largest counties in the state, they have experienced only 7 tornadoes in the past 56 years. One of those tornadoes was a large F3 that occurred in the 1969 Minnesota tornado outbreak.



Average Temperatures in Minnesota in  °Fahrenheit ( °Celsius)
    Jan        Feb        Mar        Apr        May        Jun        Jul        Aug        Sept       Oct        Nov        Dec      Annual  
Alexandria8 (−13)15 (−9)27 (−3)43 (6)56 (13)65 (18)70 (21)68 (20)58 (14)45 (7)28 (−2)14 (−10)41 (5)
Brainerd6 (−14)13 (−11)26 (−3)42 (6)56 (13)64 (18)69 (21)66 (19)56 (13)44 (7)28 (−2)13 (−11)40 (4)
Duluth10 (−12)17 (−8)26 (−3)39 (4)48 (9)58 (14)66 (19)65 (18)56 (13)45 (7)31 (−1)17 (−8)40 (4)
Grand Marais14 (−10)19 (−7)28 (−2)38 (3)47 (8)53 (12)61 (16)63 (17)55 (13)45 (7)32 (0)19 (−7)39 (4)
International Falls3 (−16)11 (−12)24 (−4)39 (4)53 (12)62 (17)66 (19)64 (18)53 (12)42 (6)24 (−4)9 (−13)32 (3)
Redwood Falls13 (−11)20 (−7)32 (−0)47 (8)60 (16)70 (21)74 (23)71 (22)62 (17)49 (9)32 (0)18 (−8)46 (8)
Thief River Falls3 (−16)11 (−12)24 (−4)42 (6)56 (13)64 (18)69 (21)67 (19)56 (13)44 (7)24 (−4)9 (−13)39 (4)
Twin Cities13 (−11)20 (−7)32 (0)47 (8)59 (15)68 (20)73 (23)71 (22)61 (16)49 (9)32 (0)19 (−7)45 (7)
Winona18 (−8)24 (−4)36 (2)50 (10)62 (17)71 (22)76 (24)73 (23)64 (18)52 (11)32 (3)23 (−5)49 (9)
Worthington11 (−12)18 (−8)29 (−2)44 (7)57 (14)67 (19)71 (22)68 (20)59 (15)47 (8)30 (−1)17 (−8)43 (6)


Average Precipitation in Minnesota in inches (millimetres)
    Jan        Feb         Mar        Apr        May        Jun        Jul         Aug       Sept       Oct        Nov        Dec      Annual  
Alexandria1.0 (25)0.7 (18)1.5 (38)1.9 (48)3.0 (76)4.5 (112)3.3 (84)3.6 (91)2.7 (69)2.2 (56)1.2 (30)0.6 (15)26.0 (660)
Brainerd0.8 (20)0.6 (15)1.5 (38)2.0 (51)3.3 (84)4.2 (107)4.1 (104)3.6 (91)2.8 (71)2.5 (64)1.6 (41).7 (18)27.7 (704)
Duluth1.0 (25)0.5 (13)1.4 (36)1.6 (41)2.3 (58)3.7 (94)3.7 (94)3.7 (94)3.7 (94)1.9 (48)1.4 (36)0.8 (20)25.6 (650)
Grand Marais0.7 (18)0.6 (15)1.1 (28)1.3 (33)2.5 (64)3.4 (86)3.4 (86)3.1 (79)3.4 (86)2.6 (66)1.8 (46)0.8 (20)24.6 (625)
International Falls0.8 (20)0.6 (15)1.0 (25)1.4 (36)2.6 (66)4.0 (102)3.4 (86)3.1 (79)3.0 (76)2.0 (51)1.4 (36)0.7 (18)23.9 (607)
Redwood Falls0.7 (18)0.6 (15)1.7 (43)2.5 (64)3.1 (79)4.1 (104)3.8 (97)3.6 (91)2.5 (64)1.9 (48)1.6 (41)0.6 (15)26.6 (676)
Thief River Falls0.2 (5)0.3 (8)0.4 (10)1.0 (25)2.6 (66)3.4 (86)3.4 (86)3.1 (79)2.4 (61)1.7 (43)0.9 (23)0.3 (8)19.7 (500)
Twin Cities1.0 (25)0.8 (20)1.9 (48)2.3 (58)3.2 (81)4.3 (123)4.1 (104)4.1 (104)2.7 (69)2.1 (53)1.9 (48)1.0 (25)29.4 (747)
Winona1.4 (36)0.7 (18)1.8 (46)3.5 (89)3.9 (99)4.2 (107)4.4 (112)4.7 (119)3.9 (99)2.2 (56)2.2 (56)1.3 (33)34.2 (869)
Worthington0.7 (18)0.6 (15)1.9 (48)2.7 (69)3.4 (86)4.6 (117)3.6 (91)3.5 (89)2.6 (66)2.0 (51)1.7 (43)0.7 (18)27.8 (706)


The U.S. Pond Hockey Championships are played every January on Lake Nokomis in Minneapolis
Even though winter does not officially start until late December, Minnesota usually begins experiencing winter-like conditions in November, sometimes as early as late October. As with many other Midwestern states, winter in Minnesota is characterized by cold (below freezing) temperatures and snowfall. Weather systems can move in from the north, west, or south, with the majority of the weather being driven in from the north. A vigorous jet stream brings high and low-pressure systems through in quick succession, which can cause large temperature variations over a short period of time.

As the last remnants of summertime air in the southern U.S. start to lose their grip, cold polar air building up in northern Canada starts to push farther south, eventually spreading into Minnesota. By the time December and January arrive, Minnesota is fully engulfed in the polar air and is then subjected to outbreaks of arctic air masses. Because there are no natural barriers north or northwest of Minnesota to block arctic air from pouring south, Minnesota gets regular shots of the arctic air through the winter. High pressure systems which descend south from the Canadian plains behind the fronts bring light winds, clear skies, and bitterly cold temperatures. The northern part of Minnesota gets the brunt of the cold air. International Falls, sometimes called the "Icebox of the nation", has the coldest average annual temperature of any National Weather Service first-order station in the contiguous United States at 37.4 °F (3.0 °C). Tower, Minnesota, sinks below zero (−17 °C) an average of 71 times per year, and the ten coldest counties in the country, based on January minimums, are all located in Minnesota. The air mass then slowly moderates as it moves south into the rest of the state. Alberta clippers alternate with these high-pressure systems, bringing high winds and some snowfall with them.
A wintry, February day in St. Paul
Minnesota occasionally gets breaks from the polar and arctic air when a zonal flow takes hold. This means that the jet stream will move in a west to east motion—rather than north to south—and warmer air from the western United States is pushed into the region. In Minnesota this pattern commonly leads to a prolonged period of above freezing high temperatures that gives Minnesotans a break from the winter freeze. Storms that move into Minnesota from a more westerly direction generally do not bring significant amounts of precipitation with them.

Winter precipitation comes in a few different forms. Snow is the main form of precipitation, but freezing rain, ice, sleet and sometimes even rain are all possible during the winter months. Larger storm systems, often Panhandle hooks or other storms that occur with a meridional flow, can bring large amounts of snow and even blizzard conditions.

Alberta clippers

Typical winter storm tracks in Minnesota.
Alberta clippers are fast-moving areas of low pressure that move through Minnesota during the winter months. Clippers get their name from Alberta, Canada, the province from which they begin their southward track. (Other variations of the same type of storm systems are "Saskatchewan Screamers" or "Manitoba Maulers".) Although clippers often originate over the northern Pacific Ocean, they lose most of their moisture through orographic lift when they collide with the Canadian Rockies. Because of the limited moisture content and quick movement of the systems, clippers rarely produce more than 6 in (15 cm) of snow as they pass through Minnesota. The biggest effects of an Alberta Clipper are what follows them, and that is arctic air, high wind speed, and dangerous wind chills. This often results in severe blowing and drifting snow, and sometimes even blizzard conditions. Alberta Clippers often proceed to become copious lake-effect snow producers on the southern and eastern shores of the Great Lakes.

Panhandle hooks
In terms of their characteristics, Panhandle hooks are nearly the opposite of Alberta clippers. Instead of forming in the north and dropping south, these low pressure systems form in the southwestern United States and then move northeast. They get their name from the location where they usually make their turn to the north; near the panhandles of Oklahoma and Texas. Unlike clippers, these storms usually have a great deal of moisture to work with. As the storms make their turn to the north, they pull in moist air from the nearby Gulf of Mexico and pull it northward toward Minnesota and other parts of the Midwest.[ As these systems move to the northeast, there will usually be a heavy band of snow to the northwest of the low pressure center if there is enough cold air present. A wintery mix of precipitation, rain, or sometimes even thunderstorms will then often occur to the south of it. Snowfall over a foot (30 cm) is not uncommon with a panhandle hook, and because of the high moisture content in these systems the snow is usually wet and heavy. Large panhandle hooks can become powerful enough to draw in arctic air after they pass by the state, leaving bitter cold temperatures and wind chills in their wake. Panhandle Hooks are responsible for some of the most famous blizzards that have occurred in the Midwest, including the Great Storm of 1975.


A Minnesota wetland during the month of April
Spring is a time of major transition in Minnesota. As winter nears its end, the sun rises higher in the sky and temperatures begin to moderate. As this happens much of the Midwest starts to experience severe thunderstorms and tornadoes. Storm systems that move inland from the Pacific begin to collide with the increasingly warm and moist air from the Gulf of Mexico. In the early part of the spring, Minnesota is usually not in a geographically favorable position to experience severe weather since the warm air needed for it has not yet pushed that far to the north. Early spring tornado outbreaks do occur occasionally in Minnesota though, as evidenced by the 1998 Comfrey – St. Peter tornado outbreak on March 29, 1998. More often, Minnesota is on the northern (cooler) side of major storm systems in the early spring, which instead results in only rain and possibly snow. Even though the winter snow pack typically starts to melt in southern Minnesota in early March, there is usually still enough cold air present over Canada to allow for major snow storms in Minnesota until late April.

Wind turbines in western Minnesota
As spring progresses, the jet stream starts to push storm systems farther to the north, and southern Minnesota becomes more prone to severe thunderstorms and tornadoes. As spring moves into the later stages, the chances for snow continue to drop and eventually disappear, south to north. By the time it gets warm enough for severe weather in northern Minnesota, the strength of storm systems have usually started to decrease, which results in fewer severe storms in northern Minnesota compared to the southern part of the state.

With the exception of areas along the shores of Lake Superior, winds in Minnesota generally prevail from the north and northwest in the winter, and south and southeast in the summer. On average, fall and spring are the windiest times of the year in Minnesota. October is the windiest month in northwest Minnesota, while April is the windiest over the rest of the state. Winds generally average between 9–11 mph (14–18 km/h) across the state, with one major exception. The heaviest winds in the state are found on the Buffalo Ridge, or Coteau des Prairies, a flatiron-shaped area extending from Watertown, South Dakota, diagonally across southwestern Minnesota and into Iowa. Created by two lobes of a glacier parting around a pre-existing plateau during the (Pleistocene) Ice Age, the Buffalo Ridge is ideal for wind power generation, with average wind speeds of 16.1 mph (26.8 km/h).


A bridge connecting East Grand Forks, Minnesota, to Grand Forks, North Dakota, is submerged during the record flooding of the Red River  in 1997.
Minnesota is prone to flooding in its major rivers by spring snowmelt runoff and ice jams. Spring flooding to some degree occurs almost annually on some Minnesota rivers, but major floods have occurred in 1965, 1969, 1997, 2001, and 2009. The flooding in 1965 was the worst flood in Minnesota history on the Mississippi River, while the flooding in 1997 was the worst in history on the Red River. The Red River flood of 1997 was aided heavily by the 11 blizzards that struck Minnesota that winter. Besides heavy winter and spring snowfall, cold winter temperatures and heavy fall and spring rains causing sudden run-off surges are also common causes of spring river flooding in Minnesota.

Minnesota is also prone to both river flooding and localized flash flooding by extended periods of heavy late-spring and summer rainfall. The Great Flood of 1993 on the Mississippi River was caused by copious amounts of rain that fell after the spring snow melt.[47] The 2007 Midwest flooding, which affected the hilly Driftless area of southeast Minnesota was the result of a training pattern of storms mixing warm moist air from Tropical Storm Erin with cooler Canadian air, resulting in record 24-hour rainfall totals of up to 17 inches (432 mm).


Canoes ready for use on a summer afternoon at Lake Harriet in Minneapolis
During a Minnesota summer, heat and humidity predominate in the south, while warm and less humid conditions are generally present in the north. A main feature of summer weather in Minnesota and the Midwestern United States as a whole is the weakening of the jet stream, leading to slower movement of air masses, a general increase in the stability of temperatures, and less wind. The strong wind that does blow almost always comes from the south, bringing in warm temperatures and humidity. These humid conditions and a jet stream that has pushed into the northern parts of the U.S. help kick off thunderstorm activity 30–40 days per year.


Showy ladyslippers bloom during the summer in Voyageurs National Park.
Daily average summer temperatures in Minnesota range from the low 70s (22 °C) in the south to the mid 60s °F (19 °C) in the north. Because summer time air masses are not as volatile as in the winter, daily high and low temperatures rarely vary more than 15 degrees (7 °C) either side of normal. While summertime around much of the country means long stretches of hot and humid weather, Minnesota is located far enough north where shots of cooler, drier polar air frequently move in behind polar fronts dropping south from Canada. The polar air typically does not stick around very long though and is quickly replaced by the warmer and more humid air from the Gulf of Mexico once again. The cool, dry polar air colliding with hot and humid summertime air keep the threat of thunderstorms and tornadoes around in Minnesota through July and August. Northern Minnesota is considerably cooler and less humid than southern Minnesota during the summer months. For example, Duluth's annual average temperature and dew point are 6 degrees (3.4 °C) cooler than Minneapolis'.
July is the hottest month in Minnesota state-wide and is usually the month when the peak heat waves occur. In July 1936, Minnesota and the rest of the Midwest suffered through its most severe heat wave on record. Most of the state was engulfed in 100 °F (38 °C) temperatures for several days in a row, and Minnesota's all time record high temperature of 114 °F (46 °C) was tied during this stretch. This heat wave was also responsible for setting the Twin Cities' all time record high of 108 °F (42 °C), as well as the all time record high of several other cities across the state.
The region of Minnesota that experiences the hottest summer temperatures is the west. Coteau des Prairies can heat cities to the north of it similar to how places in the Rocky Mountains are warmed by Chinook winds. As southwest winds blow down the slope of Coteau des Prairies, the air compresses and warms. This makes the already hot air even hotter and often causes places like Beardsley and Moorhead to record the warmest temperature in the state, despite their higher latitudes.


A flash flood in Rochester during the 2007 Midwest flooding.
The summer months of June, July and August account for nearly half of the annual precipitation total across the state of Minnesota. Most of this rain falls from thunderstorms, a frequent summer occurrence. Even though summer is the primary season for Minnesota to experience thunderstorms, they can occur from March to November. These storms can become severe, producing large hail, strong tornadoes, and large bow echos that result in damaging straight-line winds. Minnesota has experienced several major derecho events, most recently the Boundary Waters-Canadian Derecho which blew down millions of trees in the Boundary Waters Canoe Area Wilderness on July 4, 1999.
Summertime thunderstorms are fueled by dew points that often reach into the 70s °F (21 °C) and sometimes even 80 °F (27 °C). In addition to severe conditions, thunderstorms produce heavy rain and cloud to ground lightning. Heavy rain brings flash floods to Minnesota an average of three days per year. With the exception of hail, summer precipitation in Minnesota is almost always in the form of rain. The lone exception is in far northern Minnesota, where in mid-September, small amounts of snow become a possibility.


Southern Minnesota is located on the edge of Tornado Alley
Droughts are an annual summer concern in Minnesota, especially for farmers. The growing season (which varies from 90 days per year in the Iron Range to 160 days in southeast Minnesota) is when Minnesota averages its highest percentage of annual precipitation, so a lack of rainfall during this time period can be devastating to crops. The last major drought in Minnesota was in 1988. During that year, the period of April–July was the 2nd driest in the previous century, and the period of May–August was the hottest on record. The combination of dry skies and heat caused a severe drought which cost the state approximately 1.2 billion dollars in crop losses.
Other memorable drought years were 1976 and the Dust Bowl years of the 1930s. During the dust bowl, inappropriate farming techniques enhanced by years of drought conditions led to dust storms in Minnesota and the other parts of the Midwest. Drought conditions also have helped spawn forest fires. In 1894 the Great Hinckley Fire destroyed Hinckley killing an estimated 459 people, and in 1918 a forest fire killed 453 people in the vicinity of Cloquet. More recently, in 2006, the Cavity Lake Fire burned 31,830 acres (129 km²) in the Boundary Waters Canoe Area Wilderness.


An F3 tornado in southern Minnesota on August 24, 2006
Tornadoes are possible in Minnesota from March–November, but the peak tornado month is June, followed by July, May, and August. Tornadoes are most common in the southern half of the state, which is located on the northern edge of tornado alley. Just over a third of tornadoes in Minnesota strike between 4:00 pm–6:00 pm. The state averages 24 tornadoes per year; 99% of which have ratings of F2 or weaker. On average Minnesota has an F5 tornado once every 25 years. Some of the notable Minnesota tornadoes and outbreaks are:
August 21, 1883: An F5 tornado struck Rochester, killing 37. This tornado led to the construction of a new hospital, which eventually evolved into the Mayo Clinic.
April 14, 1886: A large tornado struck Sauk Rapids, killing 72. This was Minnesota's deadliest tornado on record.
June 22, 1919: The second-deadliest tornado in Minnesota history tore through Fergus Falls, killing 59.
May 6, 1965: Four F4 tornadoes ripped through the Twin Cities metro area (two of them in Fridley), killing 13.
June 16, 1992: Minnesota experienced its second-largest tornado outbreak with 27 recorded twisters. The largest tornado in this family was an F5 that struck Chandler, Minnesota, killing one. This is the most recent F5 tornado to strike the state.
March 29, 1998: An F4 and an F3 tornado that were part of a larger outbreak tore through the towns of Comfrey and St. Peter. They killed two and caused damage in the millions of dollars in Minnesota's earliest recorded tornado outbreak.
June 17, 2010: Three EF4 and six EF3 tornadoes were part of 48 twisters that touched down in Minnesota's largest tornado outbreak on record.


Early fall in Voyageurs National Park.
Autumn weather in Minnesota is marked by the rapid decrease of severe thunderstorms, dramatic cooling, and eventually the possibility of blizzards. With summer-time heat still prevalent in the southern U.S. and colder air quickly taking hold in Canada, Minnesota can be affected by wide temperature swings in short periods of time. Because of this, the jet stream, which tends to weaken during the summer months, begins to re-strengthen. This leads to quicker changes in weather patterns and increasingly strong storm systems. As autumn moves on, these storm systems bring with them progressively colder air, eventually changing the rain over snow, generally starting in October in the northern part of the state and November in the south. From September to December the average temperature in the state falls by approximately 43 °F (23 °C), the largest such temperature swing within any Minnesota season.

Blue skies and bright leaves during a Minnesota autumn.
By late October and November atmospheric dynamics are generally in place to allow storm systems to become very intense. In fact, Minnesota's all time record low pressure was recorded during fall on October 26, 2010. If these powerful storm systems are able to draw enough cold air southward from Canada, they can evolve into powerful blizzards. Some of Minnesota's most memorable winter storm events have occurred during the middle part of the fall season. On November 11, 1940, the southeast half of Minnesota was surprised by the Armistice Day Blizzard. Temperatures in the 60s °F (16 °C) on the morning of November 11 dropped into the single digits (below –12 °C) by the morning of November 12, bringing with them 27 inches (69 cm) of snow and 60 mph (100 km/h) winds. Known deaths in this blizzard reached 154, 49 of them in Minnesota. On October 31, 1991, much of Minnesota was hit by the Halloween Blizzard. A band of snowfall of 24+ in (60+ cm) fell from the Twin Cities north to Duluth. It was the single largest snowfall ever recorded in many communities across eastern Minnesota.
Image and popular culture

Culture of Minnesota

The ice castle at the 2004 St. Paul Winter Carnival.
Minnesota's climate has done much to shape the image of the state. Minnesotans boast of their "theater of seasons", with a late but intense spring, a summer of water sports, a fall of brilliantly colored leaves, and a long winter with outdoor sports and activities.
"Summer at the lake" is a Minnesota tradition. Water skiing was invented in Minnesota by Ralph Samuelson, and the Minneapolis Aquatennial features a milk carton boat race. Contestants build boats from milk cartons and float them on Minneapolis area lakes, with recognition based more on colorful and imaginative designs than on actual racing performance.
But while Minnesota's warm summers provide its natives and tourists with a variety of outdoor activities, the state is known for its winters. The state has produced curlers, skiers, and lugers who have competed in the Winter Olympics, pioneers who invented the snowmobile, and legions of ice fishing enthusiasts.

Ice fishing in Minnesota has been a theme in Hollywood films.
The state is also known for enthusiastic ice hockey players, both at the amateur and professional levels. Eveleth, Minnesota, home to the United States Hockey Hall of Fame, boasts of the number of quality players and the contributions of the city (and the rest of the Mesabi Range) to the growth and development of hockey in the United States.
To many outsiders, Minnesota's winters appear to be cold and inhospitable. A World War II newscaster, in describing the brutally cold conditions of the Russian front, stated that at least Minnesotans could understand it. A New York journalist visited St. Paul and declared that the city was "another Siberia, unfit for human habitation." In response, the city decided to build a huge ice palace in 1886, similar to one that Montreal had built in 1885. They hired the architects of the Canadian ice palace to design one for St. Paul and built a palace 106 ft (32.3 m) high with ice blocks cut from a nearby lake. This began the tradition of the Saint Paul Winter Carnival, a ten day festival which celebrates Minnesota's winter season.
Minnesota's winters are the setting of several Hollywood films, including the ice fishing comedies of Grumpy Old Men and Grumpier Old Men, set and filmed in the state. The 1996 film noir Fargo also features the backdrop of a Minnesota winter, but like most of the characters in the movie, the climate is portrayed as bleak and inhospitable.
Summer resorts on Minnesota's "10,000 lakes" may prefer to emphasize warm-season activities, but from The Rocky and Bullwinkle Show's Frostbite Falls, Minnesota to Fargo, long and cold winters seem to be the popular image of the climate of Minnesota.

See also
Climate of United States