Erratic wind and heat gripping a swath of California from San Jose to the Oregon border drove the flames.
Clearlake Oaks (California): Wind-driven wildfires destroyed buildings and threatened hundreds of others on Sunday as they raced across dry brush in rural Northern California.
The Pawnee Fire that broke out Saturday near the community of Clearlake Oaks has destroyed 12 buildings and threatened an additional 600 as it burned out of control across about 12 square miles (31 sq kilometers).
Authorities ordered people to evacuate all homes in the Spring Valley area, where about 3,000 people live.
"What we're stressing is that people, when they get the evacuation order, they heed it immediately and get out and stay out until it is safe to return," state Department of Forestry and Fire Protection Battalion Chief Jonathan Cox said.
"This is one of four large fires burning in Northern California. It's a good reminder that fire season is upon us."
Erratic wind and heat gripping a swath of California from San Jose to the Oregon border drove the flames, which were north of the wine country region where devastating wildfires killed 44 people and destroyed thousands of homes and businesses last October.
Farther north, a fire spanning about three-quarters of a mile in Tehama County destroyed "multiple residential and commercial buildings," Cal Fire said.
But firefighters appeared to be making good progress — the Stoll Fire was halfway contained and some evacuees were allowed to return home, authorities said.
A second fire in Tehama County consumed 5.5 square miles (14 square kilometres), but no buildings were reported burned. The so-called Lane Fire threatened 200 structures and some homes had been evacuated, Cox said.
It was 10 per cent contained.
A fire in neighbouring Shasta County grew to 1.6 square miles (4.14 sq kilometres) and was 20 per cent contained.
The so-called Creek Fire had damaged no structures but did prompt evacuations. The cause of each blaze was under investigation on Sunday.
No one was reported hurt.
More than 230 firefighters using helicopters, bulldozers and other equipment were battling the Pawnee Fire in a rugged area that made it difficult to get equipment up close.
"It's kind of the worst possible combination," Cox said. Matthew Henderson, who was in the area taking photographs, said he saw the fire jump a road at one point, briefly cutting off access to part of Spring Valley until firefighters pushed it back.