POSSUM KINGDOM LAKE, — Wildfires sweeping through parts of Texas and Oklahoma have destroyed dozens of homes and forced hundreds of people to evacuate, and although officials don’t yet know what ignited the blazes, a summer heat wave and drought have left both states with the perfect fuel: parched ground and dry vegetation.

“We’re in severe drought conditions, so just the tiniest little spark can start a wildfire,” Texas Forest Service spokeswoman April Saginor said.

The forest service warned that the weather could also hamper efforts to contain the fast-moving blaze in North Texas that destroyed at least 20 homes in a lakeside community Tuesday. The fire threatened a further 125 homes in the Possum Kingdom Lake area.

“It sounds like we’re still going to have winds today,” John Nichols, a spokesman for the service, said before dawn Wednesday.

In Oklahoma City, Deputy Fire Chief Marc Woodard said a preliminary assessment of the area early Wednesday indicated the fire had burned about 5,000 acres and destroyed some 20 homes on the city’s rural outskirts.

Blowing embers likely started the blaze, which was largely under control by late Tuesday night, Battalion Chief Felton Morgan said.

But Fire Chief Keith Bryant voiced concerns that the fire could re-ignite.

“The conditions are similar to what they were yesterday,” he said early Wednesday. “The winds are going to get up, they’re already gusting. That’ll be our concern on the fires that are still smoldering.”

Officials assessed the burn area from helicopters.

“We’re looking for specific structures that are damaged and any hot spots that might flare up. We’ll be trying to determine when the residents can be allowed to return,” Woodard said.

Emergency Medical Services Authority spokeswoman Lara O’Leary said four people, including two firefighters, were treated for minor injuries in the Oklahoma City blaze.

In Texas, part of a state highway was shut down because of tall flames and huge plumes of smoke, officials said. The fire had grown to at least 3,500 acres by Tuesday afternoon, though officials were expecting a more accurate map Wednesday morning, Nichols said.

Temperatures reached 106 degrees in the area Tuesday afternoon with winds gusting up to 28 mph, said National Weather Service meteorologist Jason Dunn. By nightfall, gusts were at about 20 mph and the temperature was around 99.

Cloud cover expected to move in overnight could help keep the winds around 10 mph, though winds as strong as 20 mph and were expected by afternoon and temperatures again could climb into the triple-digits, Dunn said.

“When you get just a little bit of wind in these dry conditions, it just doesn’t take anything to get a fire started,” Nichols said.