Atlanta has a humid subtropical climate, (Cfa) according to the Köppen classification, with hot, humid summers and mild winters that are occasionally cold by the standards of the southern United States. January averages 42.7 °F (5.9 °C), with temperatures in the suburbs slightly cooler. Warm, maritime air can bring springlike highs while strong Arctic air masses can push lows into the teens (−11 to −7 °C). High temperatures in July average 89 °F (31.7 °C) but occasionally exceed 100 °F (38 °C). Atlanta's high mean elevation distinguishes it from most other southern and eastern cities, and contributes to a more temperate climate than is found in areas farther south.
Typical of the southeastern U.S., Atlanta receives abundant rainfall, which is relatively evenly distributed throughout the year, though spring and early fall are markedly drier. Average annual rainfall is 50.2 inches (1,280 mm). Temperatures at or above 90 °F (32 °C) occur more than 40 days per year; overnight freezing can be expected over 45 days, but high temperatures that do not climb above the freezing mark are rare. Snow is not seen every year and averages 2.5 inches (6.4 cm) annually. The heaviest single storm brought around 10 inches (25 cm) on January 23, 1940. True blizzards are rare but possible; one hit in March 1993. Ice storms usually cause more trouble than does snowfall; the most severe such storm may have occurred on January 7, 1973. In 2010, Atlanta had its first white Christmas since 1882.
Extremes range from −9 °F (−23 °C) in February 1899 to 105 °F (41 °C) in July 1980. More recently, a low one degree away from the record, was observed on January 21, 1985.
In 2007, the American Lung Association ranked Atlanta as having the 13th highest level of particle pollution in the United States. The combination of pollution and pollen levels, and uninsured citizens caused the Asthma and Allergy Foundation of America to name Atlanta as the worst American city for asthma sufferers to live in.
However, the city was recently commended by bodies such as the Environmental Protection Agency for its eco-friendly policies. In 2009, Atlanta's Virginia-Highland became the first carbon-neutral zone in the United States. Verus Carbon Neutral developed the partnership that links 17 merchants of the historic Corner Virginia-Highland shopping and dining neighborhood retail district, through the Chicago Climate Exchange, to directly fund the Valley Wood Carbon Sequestration Project (thousands of acres of forest in rural Georgia).
On March 14, 2008, an EF2 tornado hit downtown Atlanta with winds up to 135 mph (217 km/h). The tornado caused damage to Philips Arena, the Westin Peachtree Plaza Hotel, the Georgia Dome, Centennial Olympic Park, the CNN Center, and the Georgia World Congress Center. It also damaged the nearby neighborhoods of Vine City to the west and Cabbagetown, and Fulton Bag and Cotton Mills to the east. While there were dozens of injuries, only one fatality was reported. City officials warned it could take months to clear the devastation left by the tornado.
Atlanta has a reputation as a "city in a forest" or a "city of trees" due to its abundance of trees, unique among major cities. The city's main street is named after a tree, and beyond the Downtown, Midtown, and Buckhead business districts, the skyline gives way to a dense canopy of woods that spreads into the suburbs. The nickname is factually accurate, as the city's tree coverage percentage is at 36%, the highest out of all major American cities, and above the national average of 27%. Atlanta's tree coverage does not go unnoticed—it was the main reason cited by National Geographic in naming Atlanta a "Place of a Lifetime":
"For a sprawling city with the nation’s ninth-largest metro area, Atlanta is surprisingly lush with trees—magnolias, dogwoods, Southern pines, and magnificent oaks.