WINTHROP, Wash. — Cooler temperatures and lighter winds are expected to descend on a wildfire-stricken Washington state, helping firefighters battle flames that have been growing unfettered for a week and have covered hundreds of square miles.
While Sunday saw only slight improvements in the hot temperatures and gusty winds that have fueled the wildfires, the forecast for Monday and Tuesday calls for lighter winds and temperatures, said Spokane-based National Weather Service meteorologist Greg Koch.
Then on Wednesday a ‘‘vigorous’’ front is expected to cover Washington, bringing rain to much of the state. But it will also bring lightning, which could ignite more fires, he added.
Officials said Sunday the wildfire burning in north-central Washington covered about 370 square miles. It measured 260 square miles on Friday.
Okanogan County Sheriff Frank Rogers estimated that 150 homes have been destroyed but suspects that number could be higher. His deputies have not been able to search parts of the county where homes are spread miles apart. No serious injuries have been reported, Rogers said.
There are nearly 1,400 firefighters battling the flames, assisted by more than 100 fire engines, helicopters dropping buckets of water, and planes spreading flame retardant.
On Sunday, Rogers was driving to the town of Twisp to survey the damage.
‘‘It’s the first time in four days I’ve seen blue sky,’’ he said. ‘‘Every day, when you got up, it was nothing but smoke. All we’ve seen of the sun is a red ball.’’
Although the weather is improving, the towns in the scenic Methow Valley remain without power and have limited landline and cellphone service. Okanogan County Public Utility District officials told KREM TV that fully restoring power to the area could take weeks.
Governor Jay Inslee said Friday about 50 fires were burning in Washington, which has been wracked by hot, dry weather, gusting winds, and lightning. About a dozen helicopters from the Department of Natural Resources and the National Guard, along with a Washington State Patrol spotter plane, were assisting firefighters.
Karina Shagren, spokeswoman for the state’s Military Department, said 100 National Guard troops were on standby.