Atlanta, Georgia, is located at an interesting place, because it is just above the 'border' where two different air masses collide. So depending on the time of year, there can be either continental, moderate (in winter cold), air masses (for most of the year) or maritime tropical, warm, moist, air masses when the storm season is on, and the air masses from the Caribbean see go deeper inland. Note that none of them form over Atlanta, but are forming in other places and are coming towards it.