The timing couldn't be worse as seasonal firefighters return to college and other jobs elsewhere.

In the past week more than 100 requests for 20-person fire crews went unfilled in Washington and Oregon, said Kathy Fletcher, spokeswoman for the Northwest Interagency Coordination Center in Portland, Ore.

At the Yakama Indian Reservation in central Washington, fire managers waited for more crews to arrive to help fight a lightning-caused fire that spread rapidly in remote, rugged forest. In the central Cascade Range, the Polallie fire burned unabated for lack of local firefighters as fire managers waited for a national crew to arrive.

The center estimates state and federal agencies, as well as contract fire crews, are losing 15 percent of their firefighters as they return to college and jobs in the next few weeks, while forecasters predict more of the same hot, dry weather.

"The extended forecast indicates no relief," Fletcher said. "The good news is the days are getting shorter and the nights are getting cooler, which helps in the firefighting efforts."

On Thursday, the two top priority wildfires for national resources were in Washington state with more than 3,000 firefighters assigned to the Tripod complex and Columbia complex.

The lightning-caused Columbia complex near Dayton has blackened 150 square miles of wheat fields, brush and forest in southeastern Washington and was 45 percent contained.

In northcentral Washington, firefighters continued to battle the massive Tripod complex about seven miles northwest of Winthrop. One of three wildfires in the Pasayten Wilderness Area, the Tripod complex has burned nearly 258 square miles.

At its northern flank, the fire was burning more than a mile south of the Canadian border. No structures were immediately threatened, and the blaze was 56 percent contained.

The Tatoosh complex, 18 miles northwest of Mazama, was estimated at 34,000 acres and extended into Canada. U.S. and Canadian fire managers also were monitoring the Van Peak fire, which was burning between the Tripod and Tatoosh fires about five miles south of the border.

Residents in Mazama remained on notice to be ready to evacuate if the Cedar Creek fire grows. That blaze, estimated at about two square miles or 1,450 acres southwest of town, was 40 percent contained.

Farther south, some residents in the remote hamlet of Stehekin at the north end of Lake Chelan were warned - yet again - they might have to flee the Flick Creek fire. The fire, estimated at 6,397 acres, has been threatening the town intermittently since it was accidentally started by a campfire July 26.

The town of about 100 full-time residents is reachable only by boat, float plane, horse or on foot.

The fire on the east side of the lake was backing down the Hazard Creek drainage toward Stehekin but remained about a mile away from the boat landing, fire information officer Betty Higgins said.

"Water is being dropped right below the fire to calm it down, but we do have hot and dry conditions," Higgins said.

The Tinpan fire in the Glacier Peak Wilderness grew to 8,113 acres, or more than 12 square miles. Roughly 108 firefighters were assigned to the blaze.

Additional firefighters and resources arrived Thursday at some of the newer blazes, all caused by lightning. Twenty firefighters worked to protect structures near the Polallie fire, 15 miles northwest of Cle Elum in the Alpine Lakes Wilderness.

The fire forced the closure of Cle Elum Valley, a box canyon with more than 25 summer homes and several campsites.

A state crew arrived Thursday to assist tribal, local and federal firefighters on the Yakama reservation. Lightning earlier this week started three fires on the reservation, all in a rural area near the Klickitat River. One was contained, said Edwin Lewis, forest manager for the Bureau of Indian Affairs.

No structures were threatened.

Fire managers urged people to be aware of conditions and restrictions on public lands. Numerous trail and road closures and campfire restrictions have been imposed, most recently a ban on open campfires throughout the sprawling Mount Baker-Snoqualmie National Forest, which covers the western half of the northern and central Cascades.

"With the extension of fire season, folks should be safe - know where they're going and what they're getting into," Fletcher said. "That's always true, but even more so now."