Flash flood warnings were posted for much of the eastern Sierra Nevada on Wednesday as the National Weather Service predicted a 40 percent chance of rain over a cluster of wildfires in Plumas National Forest.
Fire officials worried that crews battling a 22,000-acre blaze about 125 miles northeast of Sacramento could face mudslides on burned-over slopes.
That blaze was only about 20 percent contained late Tuesday, after afternoon lightning sparked some new spot fires on the parched terrain, fire information officer Jill Poulsen said.
Elsewhere in the Sierra, crews in the Inyo National Forest were busy trying to control new spot fires and gained little on a 35,000-acre wildfire, roughly 55 square miles, which was about 80 percent contained Tuesday, said U.S. Forest Service spokeswoman Nancy Upham.
The fire, sparked by lightning on Friday, has destroyed six homes in an area north of Mount Whitney. Eleven firefighters have been injured.
Large wildfires were active in 12 Western states, according to the National Interagency Coordination Center.
Five of the top priority wildfires are in Utah, where crews are fighting the biggest fire in state history, which had spread across 514 square miles by early Wednesday, authorities said. The fire about 120 miles south of Salt Lake City was 30 percent contained Wednesday.
Utah fire teams also were on alert for a storm front expected to arrived Wednesday that could deliver more high wind and dry lightning.
Nevada's largest blaze — near the Idaho line — grew to about 114 square miles and was about half contained, Elko Interagency Dispatch Center Manager Bill Roach said.
The weather was cool and cloudy in the southwest corner of South Dakota, where crews expected to make significant progress on a wildfire near Hot Springs that killed a homeowner and destroyed 30 houses. The blaze had covered more than 15 square miles and was 20 percent contained.
Another round of record heat was forecast in the Northwest, adding to the problems faced by crews battling fires in Washington. High temperatures ranging up to 107 degrees were forecast for Thursday and Friday in south-central Washington, and Wednesday's forecast high in Seattle, on the usually cooler side of the state, was 97 degrees.