Some of the biggest blazes were near Georgia's coast on Wednesday, while others were popping up in northern Florida, a state facing one of its worst fire seasons in decades.
It was not yet clear how the wildfires started, but the bottom half of Georgia is perilously dry and the conditions prompted the state's forestry commission to issue a burn ban for the first time ever.
Southeastern Georgia has seen just 30cm of rain since the beginning of September — almost 40cm below normal, the National Weather Service said.
The fires spread so quickly in that area that residents received no warnings or alerts.
Georgia's two biggest wildfires together have burned more than 85 square kilometres and at least four other smaller fires have been reported in the state.
The fast-moving Brantley County fire threatened around 1000 homes on Wednesday after destroying dozens a day earlier.
That fire grew by around six times in just 12 hours on Tuesday. So far no major injuries have been reported.
The rural county is about midway between Georgia's coastal beaches and the Okefenokee Swamp, dotted with livestock and fruit farms as well as thick stands of planted pines grown for timber.
Crews worked to create fire breaks and stop the flames from reaching populated areas. The biggest concern was gusting winds that could easily spread embers.
Authorities said rain is desperately needed. The area with the worst fires was in exceptional or extreme drought, the most dire levels, according to the US Drought Monitor.
Pine and hardwood forests in the region are helping charge the fires, and swampy lowlands with thick layers of leaves and woody debris are super flammable when they dry out.
The commission's 30-day burn ban is for the southern part of the state.
FEMA announced the approval of grants for Georgia and Florida to battle the blazes.
Georgia Governor Brian Kemp declared a state of emergency for more than half of the state's counties.
More people were told to evacuate from Brantley County on Wednesday afternoon, on top of the 800 evacuations previously. Another large fire that started in nearby Clinch County also prompted evacuations.
In Florida, firefighters battled more than 130 wildfires that burned 100 square kilometres, mostly in the state's northern half.
"Florida has got one of the worst fire seasons in maybe the last 30 or 40 years, or it's turning out to be that way," state Commissioner of Agriculture Wilton Simpson said.
"We've been in drought for 18 months now all across the state."
The National Weather Service said a dangerous combination of low humidity and breezy winds would keep the fire danger elevated Wednesday.
Smoke drifted to Atlanta, Savannah, Georgia, and Jacksonville, Florida. The air quality in parts of south Georgia declined to the unhealthy category, meaning all people there might feel health effects.
Smoky conditions were expected to linger throughout the Atlanta area, according to the Atlanta-Fulton County Emergency Management Agency. The worst fires were more than 320km southeast of the city.
Smoke from Georgia fires also spread into South Carolina, according to its forestry commission.
The high fire risk was expected to continue each afternoon through Friday due to the very dry conditions, the weather service said.
