A Northern California blaze more than doubled in size overnight despite an increase in humidity and cooler temperatures.
The California Department of Forestry and Fire Protection said the fire, which erupted Sunday several miles away from the community of Lower Lake, had burned nearly 30 square kilometers (19 square miles) by Monday.
For the second time in as many weeks, residents had to evacuate their homes because of the uncontained fire lighting up rocky hills about 160 kilometers (100 miles) north of San Francisco.
More than 1,100 firefighters are battling the blaze, w hich is threatening 50 structures.
No homes have been destroyed and no injuries have been reported.
Meanwhile, firefighters have nearly surrounded a larger blaze that started about two weeks ago and burned 175 square kilometers (109 square miles).
That fire destroyed 43 homes, but all evacuations have been lifted. Students in the Middletown Unified School District, in Lake County, California, could start classes next Tuesday, but it might be later depending on where the fire burns.
Fire officials are investigating the causes of both fires. There have been five arson arrests related to smaller fires in five weeks.
Other western state fires:
A U.S. Forest Service firefighter was killed in the Lake Tahoe area after he was struck by a tree while battling a wildfire -- the second firefighter killed in a California blaze since the summer wildfire season got underway.
Michael Hallenbeck, 21, of Shingle Springs, California, was hit Saturday during the initial attack on a fire that broke out south of the Echo Summit mountain pass.
On July 30, a firefighter was killed by a wildfire in the Modoc National Forest while he scouted the area for ways to fight the blaze. Forest Service firefighter David Ruhl, of Rapid City, South Dakota, had been on temporary assignment since June in California.
On Sunday, hundreds of people turned out in Rapid City to pay their respects at a procession and memorial service for Ruhl. Forest Service Associate Chief Mary Wagner attended, saying Ruhl's death was "felt by every member of the Forest Service."
Authorities lifted evacuation orders for most of the 1,000 homes threatened by a wildfire near the Arizona-California line, one of several blazing across the tinder-dry West.
The fire in Arizona's Mohave Valley area chewed through 26 square kilometers (10 square miles) and remained uncontrolled Monday.