The National Weather Service also issued a red-flag warning for extreme weather conditions with the possibility of thunderstorms and lightning that could spark new fires east of the Cascades, beginning Tuesday evening and continuing through Thursday.
And Commissioner of Public Lands Peter Goldmark banned all outdoor fires on lands protected by the Washington State Department of Natural Resources.
Nearly 1,700 firefighters were working to control two wildfires already burning, including a blaze that has destroyed three homes and several outbuildings.
The Colockum Tarps Fire has burned across more than 73 square miles of grass, sagebrush and timber southeast of Wenatchee in the Colockum Pass area. The fire was 5 percent contained, but the flames spread rapidly Tuesday, churning through dry fuels to the south, fire spokesman Peter Frenzen said.
The Federal Emergency Management Agency authorized the use of federal funds to help with firefighting costs for the fire burning in Chelan and Kittitas counties.
Kittitas County commissioners declared an emergency Tuesday because of the flames.
Residents of about 60 homes have been evacuated.
More than 340 firefighters were focused on protecting power lines, recreation areas, wind farms and some scattered homes south of the fire, Frenzen said.
The potential for thunderstorms also are raising fears about high winds and lightning, which could spark even more fires.
"The winds and the thunderstorms are a concern, but on the plus side, we're also looking at the possibility of some moisture by Thursday," Frenzen said.
Dry brush and grasses and moderate winds were fueling the blaze. A so-called scoop plane, which flies low to scoop up water, and an air tanker were dropping water and retardant on the fire.
The fire started Saturday. The cause was under investigation.
Further south, about 1,345 firefighters were working to control a fire that has burned across 35 square miles around Satus Pass and closed Highway 97 between Goldendale and Toppenish.
The fire was 40 percent contained Tuesday. Evacuation levels were lowered for residents of 69 homes on the fire's sound end, allowing them to return home, said Bruce Livingston, a Washington Department of Natural Resources spokesman.
A containment line was established most of the way across the southern and western end of the fire, Livingston said, and crews were focusing on the eastern edge of the blaze.
The blaze ignited last Wednesday and the cause was under investigation.