NAHUNTA, Ga. (AP) — Wildfires burning across the southeastern U.S. were intensifying Wednesday after destroying nearly 50 homes in Georgia and forcing evacuations and school closures in some communities.

Some of the biggest blazes were along Georgia's coast and between and around Jacksonville, Florida, a state that is facing one of its worst fire seasons in decades. It was not yet clear how the wildfires started, but a long drought, low humidity and strong winds were fueling them.

Georgia's two biggest wildfires together have burned more than 31 square miles, and at least four other smaller fires have been reported in the state. The area of the state where the worst fires were burning is in exceptional or extreme drought, the most dire levels, according to the U.S. Drought Monitor.

In southeast Georgia, the fast-moving Brantley County fire was threatening more homes Wednesday after destroying 47 a day earlier, according to Joey Cason, the county manager.

That fire grew in size by roughly six times in just a half day Tuesday, he said. Nearly two dozen fire agencies were helping fight the blaze, Cason said at a news conference Wednesday.

Brantley County Sheriff Len Davis warned residents to be ready to evacuate, noting that the winds could shift rapidly and unexpectedly.

At least 800 evacuations have taken place in the county and five shelters have opened, as the fire threatens 300 more homes, the Federal Emergency Management Agency said.

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Another large fire that started in Clinch County had also forced evacuations, which were underway in multiple communities, the Georgia Forestry Association said. "This is a serious and evolving situation," said Tim Lowrimore, president & CEO of the association.

In Florida, firefighters on Wednesday were battling 131 wildfires that had burned 34 square miles, mostly in the state's northern half.

Firefighting equipment was being staged across the state so resources are closer to the fires, Florida Commissioner of Agriculture Wilton Simpson said.

"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," Simpson said. "We've been in drought for 18 months now all across the state."

A wildfire disrupted Amtrak train service Monday in the northeast part of the state. Service was back to normal Wednesday, according to Amtrak spokeswoman Beth Toll.

A dangerous combination of low humidity and breezy winds will keep the fire danger elevated Wednesday, the National Weather Service said.

Smoke drifted to Atlanta, Savannah, Georgia, and Jacksonville, Florida. The air quality in parts of south Georgia declined to the unhealthy category Wednesday, meaning all residents might feel health effects.

Smoky conditions were expected to linger throughout the Atlanta area on Wednesday, according to the Atlanta-Fulton County Emergency Management Agency. The worst fires were burning more than 200 miles southeast of the city.

The high fire risk was expected to continue each afternoon through Friday due to the very dry conditions, the weather service said.

Martin reported from Atlanta. Associated Press reporters Jeff Amy and Kate Brumback in Atlanta, Mike Schneider in Orlando, Florida, and John Seewer in Toledo, Ohio, contributed.