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 6.5 square kilometers. Authorities ordered people to evacuate all homes in the Spring Valley area, where about 3000 people live.

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 - it was nearly halfway contained and some evacuees were allowed to return home, authorities said.

The largest of the fires, a second one in Tehama County, consumed14 square kilometres, but no buildings were reported burned. Some homes were threatened and some had been evacuated, Cox said, although he did not have specific numbers. It was partially contained.

A smaller fire in neighbouring Shasta County was mostly contained and had damaged no structures.

The cause of each blaze was under investigation 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.

Australian Associated Press