California fires largest in state history

A wildfire in California is now the state's largest and has razed an area the size of Los Angeles

Twin Northern California blazes fuelled by dry vegetation and hot, windy weather have grown to become the largest wildfire in state history, becoming the norm as climate change makes the fire season longer and more severe.

The two fires burning a few kilometres apart and known as the Mendocino Complex are being treated as one incident.

It has scorched 1148 square kilometres, fire officials said on Monday.

The fires, north of San Francisco, have burned 75 homes and are only 30 per cent contained.

The size of the fires surpasses a blaze last December in Southern California that burned 1141 square kilometres.

It killed two people, including a firefighter, and destroyed more than 1000 buildings before being fully contained on January 12.

Hotter weather attributed to climate change is drying out vegetation, creating more intense fires that spread quickly from rural areas to city subdivisions, climate and fire experts say.

But they also blame cities and towns that are expanding housing into previously undeveloped areas.

More than 14,000 firefighters are battling over a dozen major blazes throughout California, state Department of Forestry and Fire Protection spokesman Scott McLean said.

Crews made progress over the weekend against one of the two blazes in the Mendocino Complex with help from water-dropping aircraft, Cal Fire operations chief Charlie Blankenheim said in a video on Facebook.

But the other one is growing after spreading into the Mendocino National Forest.

The complex of fire has been less destructive to property than some of the other wildfires in the state because it is mostly raging in remote areas.

But officials say the twin fires threaten 11,300 buildings and some new evacuations were ordered over the weekend as the flames spread.

A new fire erupted Monday in Orange County, south of Los Angeles, and prompted the evacuation of two canyons and some campgrounds as it expanded into the Cleveland National Forest.

Farther north, crews gained ground against a deadly blaze that has destroyed more than 1000 homes in and around Redding. It was nearly halfway contained, Cal Fire said.

The wildfire about 360km north of San Francisco started more than two weeks ago by sparks from the steel wheel of a towed-trailer's flat tire. It killed two firefighters and four residents and displaced more than 38,000 people.

Officials began allowing some residents to return to their neighbourhoods. But tens of thousands of others remain evacuated.

Another blaze that ignited last week has damaged Northern California's historic Dardanelle resort in the Stanislaus National Forest.

The resort owners said in a Facebook post "at this point it has been confirmed that there is 'massive structural damage.' We are heartbroken and struggling with this news."