Seventh Person Dies As US Wildfires Spread

"Fire season is really just beginning."

A seventh person has died in a northern California wildfire as a couple of other fast-growing wildfires in the state expanded by more than 25 per cent overnight and continue to spread.

More residents were ordered to evacuate their homes as weary firefighters endured high temperatures and gusting winds.

The Carr fire, about 260km north of Sacramento, claimed the life of a power company lineman on Saturday, according to a CBS affiliate citing a spokesman for the PG&E Corportation. Neither a spokesman with the electric company nor fire officials were immediately available for comment.

The Carr fire, one of the most destructive in California history, had already killed six people, including a great-grandmother and two small children, and a firefighter and bulldozer operator.

Two other blazes collectively called the Mendocino Complex burned in Mendocino, Lake and Colusa counties, about 145km north of San Francisco.

The River and Ranch fires had grown to cover a total of 81,500 hectares by early Saturday, and were considered 34-per cent contained.

This year, California wildfires have burned more land earlier in the "fire season" than usual, said Ken Pimlott, Cal Fire director, during a news conference on Saturday.

"Fire season is really just beginning. What seems like we should be in the peak of fire season, historically, is really now the kind of conditions we're seeing really at the beginning," said Pimlott.

California Governor Jerry Brown, who visited some of the burned areas on Saturday, said, "This is part of a trend, the new normal, that we've got to deal with."

Through last week, California fires had torched about 117,300 hectares, more than double the five-year average over that same period, according to Cal Fire.

The Mendocino Complex fires cover more than two-thirds the size of sprawling Los Angeles.

They have forced the evacuation of more than 20,000 residents and destroyed more than 100 structures.

More evacuations were ordered on Saturday afternoon, but no estimate of people involved was released.

So far this year, US fires have burned two million hectares, much more than the 10-year average, according to the National Interagency Fire Center.