Road closures and evacuations were changing regularly, as hot weather and winds with gusts up to 30 mph were pushing the fire over ridge tops and toward a cluster of small towns northeast of Seattle.
"This is a very active and fluid situation," fire spokesman Chuck Turey said.
As of Saturday morning, the lightning-caused fire had scorched nearly 340 square miles in the scenic Methow Valley. The fire was measured at 260 square miles Friday.
People living between Carlton and Pateros have been told to leave their homes. The fire has blackened hillsides, destroyed homes and downed power lines. Many towns were without electrical power or phone service Saturday.
Officials said there are no reports of serious injuries and only one more structure was destroyed overnight by the lightning-caused wildfire.
Minor burns and bruises had been reported, but Turey called that "a pretty amazing safety record."
Airplanes and helicopters were dropping water and fire retardant on all parts of the fire, with no one area more of a concern than another, Turey said.
"We're seeing some wind shifts so that the fire is going to be pushed in some directions it hasn't been pushed to date," he said, adding that the good news is that in some places the wind is pushing the first back on itself.
Rancher Vic Stokes, 60, went to bed Friday thinking the fires had calmed down and his ranch outside of Twist was safe.
He and his family have been fighting brush fires since Thursday, getting little sleep.
By Saturday, a fire had jumped to a nearby creek bed. Stokes, his son and his daughter-in-law spent the morning clearing brush. "Anything that hasn't burned has a chance of burning yet," Stokes said.
So far, his home is intact, but he's lost hay and a barn and is worried for livestock he had grazing in an area that's now scorched.
"We need to get up there and see what we can find that's alive. We know we lost cattle," he said.
As the fire got closer to Carlton, rancher Pete Scott brought 60 cattle to his property in town from the range land. His home, a green oasis, is serving a meeting point for some of the displaced residents. "We're trying to survive," Scott said.
The fire has calmed down near Pateros, where it destroyed about 100 homes Thursday and Friday, Okanogan County Sheriff Frank Rogers said. "It's just starting to run out of places to burn," he said.
The fire has picked up on its north side closer to Winthrop, but winds have been erratic and were blowing the fire in different directions.
The blaze was burning in a sparsely populated area, with homes scattered throughout the woods and along the highway.
The Chiwaukum Creek Fire has closed U.S. Highway 2 from Coles Corner to Leavenworth.
Gov. Jay Inslee said about 50 fires were burning in Washington, which has been wracked by hot, dry weather, gusting winds and lightning. Some 2,000 firefighters were working in the eastern part of the state, with about a dozen helicopters from the Department of Natural Resources and the National Guard, along with a Washington State Patrol spotter plane.
Karina Shagren, spokeswoman for the state's Military Department, said 100 National Guard troops were on standby, and up to 1,000 more in Yakima could receive additional fire training. Active duty military could be called in as well, Inslee said.
Also on Saturday, authorities announced that they are bringing in two military air tankers from Wyoming to help fight wildfires in the Pacific Northwest and elsewhere. Officials at the National Interagency Fire Center in Boise, Idaho, say the tankers were activated to ensure that firefighters had adequate air tanker capability in the region.