OLYMPIA, Wash. Aug 14 (Reuters) - Firefighters in Washington state fought a wildfire on Tuesday that has destroyed 60 homes and burned more than 20,000 acres (8,093 hectares) between two national forests east of the capital, Olympia.
Another 400 homes were evacuated in the rolling hills between Cle Elum and Ellensburg, two towns in northwest Washington at the eastern edge of the Cascade Mountains.
The massive blaze was among more than a dozen wildfires burning across the U.S. West, which is wilting under a heat wave that has sent temperatures into the triple digits. Together, the fires have singed around 230,000 acres (93,000 hectares) across Idaho, Washington and California.
Authorities suspect the Washington state fire began at a construction site east of Cle Elum, about 75 miles (120 km)southeast of Seattle.
"We don't know the cause, we just know the origin," said Rick Scriven, a spokesman for a state emergency response team at the scene.
With strong winds expected to pick up Tuesday afternoon and no rain in the area for three weeks, more damage is likely, said Bryan Flint, spokesman for the Department of Natural Resources.
The fire is likely to spread to the north, where it could reach the Wenatchee National Forest within 10 miles (16 km), and to the east, which is mostly farmland, Flint said. South of the fire is the Snoqualmie National Forest.
"It's going to be a changing situation all day long," Flint said. "This fire is by no means over with."
In Northern California, more than 1,100 firefighters spent a third day attacking a pair of wildfires that have destroyed two homes in Lake County's Spring Valley area and charred some 7,000 acres (2,832 hectares).
Daniel Berlant, a California Department of Forestry and Fire Protection spokesman, said firefighters had contained only 30 percent of the two blazes burning dry brush in remote Lake and Colusa counties and did not expect full containment for a week.
But firefighters made enough progress attacking one of the fires that authorities lifted an evacuation order for 480 homes in the Spring Valley area on Monday night, he added.
Berlant said the fires had moved east into Colusa County and continued to threaten the area around Wilbur Hot Springs, a resort that offers clothing-optional bathing in mineral water. The resort closed on Sunday for 12 days of maintenance and it was not clear if anyone had been forced to flee.
Two firefighters suffered minor injuries while working the blaze in triple-digit temperatures. Berlant said California had experienced a significant increase in fires this year.
Suzann Thompson, who works the front desk at Clear Lake Cottages and Marina in Clearlake, said the fires decimated business throughout the area. Clear Lake, the biggest lake in California, is a popular tourist attraction.
"It's really a catastrophe," she said.
In Idaho, fire crews struggled to contain a dozen blazes raging across more than 200,000 acres (80,937 hectares) of steep, forested terrain. A 20-year-old U.S. Forest Service firefighter was killed in Idaho on Sunday when a tree fell on her, U.S. Forest Service spokeswoman Elizabeth Slown said.
Smoke and ash pouring into communities from the state capital of Boise to the ranching community of Salmon in east central Idaho caused health officials to caution against undue exertion outdoors because of poor air quality.
Robyn Broyles, spokeswoman for the National Interagency Fire Center in Boise, said several blazes in Idaho's mountains were far from contained and likely would not be extinguished "until the snow flies."
Wildfires have consumed roughly 6 million acres across the nation this year. That compares to the 10-year average of 4.9 million acres, according to figures from the interagency fire center. (Additional reporting by Ronnie Cohen, Laura Zuckerman and Dan Whitcomb; Editing by Stacey Joyce; Writing by Dan Whitcomb)