Geography of Atlanta

[4] The climate of Atlanta and its metropolitan area is humid subtropical (Cfa) according to the Köppen classification, with four seasons including hot, humid summers and cool winters that are occasionally cold by the standards of the southern United States; the city and its immediate suburbs are located in USDA Plant Hardiness Zone 8a, although the far northern suburbs begin to transition to Zone 7b.

[6] 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.

Despite having far fewer rainy days, average yearly rainfall is higher here than in the Seattle area, especially due to heavy thunderstorms and occasional tropical depressions.

[6] True blizzards are rare but possible; the Storm of the Century, which affected the region on March 12–14, 1993, is one such example, bringing snowdrifts up to 6 ft (1.8 m) high in some parts of north Georgia.

Later that same winter (the third-coldest ever), a major snow-and-ice storm almost prevented the inauguration of the new governor of Georgia, and crippled the region for two days, with snow still left more than a week later in some places.

Some palm trees like palmetto and cacti like prickly pear can withstand the cold nights, complementing numerous flowering pansies and a few camellias, and other mild-winter-friendly plants of the region.

This east or northeast wind will often blow down into the metro area in winter or even spring (sometimes fall and very rarely summer), dramatically lowering the temperature and bringing clouds and often fog or mist, along with a swift breeze.

In winter this can be a curse, bringing freezing rain to exposed objects on the north and/or east sides of town, and occasionally very dangerously to the ground and roads.

Later in the spring however, it can be a great blessing, as it often protects the area from severe thunderstorms and tornadoes, with the cool air acting like a fire extinguisher to the storms.

The local geography also plays a role in the day-to-day weather, with the shallow valleys to the southwest (rather than the mountains to the northeast) cooling rapidly on clear and calm nights, particularly when the humidity is low.

[17] Record-cool high temperatures of 64 °F (18 °C) caused by cold-air damming against the Appalachians served to eliminate the normal tornado risk in north Georgia and to weaken the storm faster than expected, reducing the anticipated damage to the area.

Less than a month later in early October 2017, the much smaller Hurricane Nate was forecast to pass rapidly through northwest Georgia as a weak tropical storm, expected to cause far fewer issues to the metro area than Irma.

Despite predictions of a warm and dry winter due to La Niña developing the following summer, additional 1.2 inches (3.0 cm) fell on December 25, giving the city (and its northern and western suburbs) its first true white Christmas in over a century.

A blizzard (see: 1993 Storm of the Century) caught much of the Southeast off-guard in 1993, dumping 4.5 inches (11.4 cm) at the Atlanta airport on March 13, and much more than that in the suburbs to the north and west, as well as in the mountains.

The following year, the first widespread winter storm since 2002 dumped 4.5 inches (11.4 cm) on March 1, with the heaviest to the southwest and east-northeast, and surprisingly little or nothing in the far northern suburbs and mountains.

Areas to the due east and west often receive more snow than metro Atlanta, because the energy begins to transfer to a coastal low in the Atlantic, on its way to becoming a nor'easter.

A mid-December 2000 snow (a record 2.5 inches (6.4 cm) for the month) was followed by very cold weather that left spots of it on the ground in shady areas until Christmas.

Paulding, northwest Cobb, and southeast Bartow counties were hit with up to 13 inches (33 cm) of very heavy and wet snow, due to the temperature being slightly above freezing for much of the event.

The well-remembered January 1973 ice storm was brutal, and was followed in February by the record-breaking 1973 Southeast U.S. snowstorm that hit the coastal half of the state, bringing light snow to what were then the far southeastern suburbs.

A January 1982 snowstorm, which came to be called "Snow Jam '82" by the media and those who lived through it, also crippled the city just as bad as ice can, striking in the afternoon while everyone was at work, several hours earlier than expected.

Tens of thousands of people were stranded in the city, abandoning cars on every road and freeway and booking hotels to capacity, unable to get home to the suburbs.

Despite this well-known experience, the same thing happened in January 2014, when snow expected to hit mainly middle Georgia in the afternoon crept northward at midday, the resulting road ice stranding children in schools and even on school buses overnight, while people slept in makeshift shelters such as Home Depot, Kroger, and CVS stores, and in fire stations and even in their vehicles.

While only 2.6 inches (6.6 cm) fell on the afternoon of the 28th, and many issues from the 2011 snow-then-ice storm had been addressed, the sudden rush of traffic between noon and 1pm rapidly created massive gridlock and prevented snow removal and deicing equipment from going anywhere.

GDOT equipment that had been dispatched to areas further down-state based on early forecasts also lessened the response, as they could not get back north to their regular districts in time.

The severe record drought which affected the region starting in late 2006 finally began to abate significantly after heavy fall rains in 2009.

The 2009 Atlanta floods affected the entire area on September 21, 2009, with parts of eastern Paulding, northern Douglas, and southwestern Cobb counties getting around 20 inches (500 mm) of rain in a week, with half of that falling in just 24 hours near the end of the period.

Flood events are localized from nearly stationary thunderstorms, or more broadly impacting from slow-moving tropical storm remnants, or sometimes from unusually heavy and persistent winter rains during El Niño years.

[citation needed] Bright spots include projects that encourage smart growth, such as the BeltLine and Atlantic Station mixed-use development, which the Environmental Protection Agency commended in 2005.

There, neighborhood merchants, through the Chicago Climate Exchange, directly fund the Valley Wood Carbon Sequestration Project (thousands of acres of forest in rural Georgia).