State officials warned people to be alert to the risk of sudden flows of debris down the scorched, denuded slopes of the foothills of the Sierra Nevada mountains.

"Although wildfire damage can be immeasurable, the danger is not over after the flames are put out," the California Department of Forestry and Fire Protection (Cal Fire) said in a statement on Tuesday.

Meanwhile US Interior Department Secretary Ryan Zinke said on Tuesday that the deadly California wildfires are partly due to lawsuits from environmentalists who have sought to stop forest management practices such as forest thinning.

"Radical environmental groups that would rather burn down the entire forest than cut a single tree or thin the forest" have brought lawsuits to stop forest management, Zinke told reporters in teleconference about the California wildfires, the deadliest in the state's history.

Zinke said other factors such as hotter temperatures, historic drought conditions and plenty of dead and dying trees also were also to blame.

Remains of 79 victims have been recovered since the Camp Fire erupted on November 8 and largely obliterated the town of Paradise, a community of nearly 27,000 people about 280km north of San Francisco. The Butte County Sheriff's Office has tentatively identified 64 of the victims.

The missing persons list kept by the sheriff's office still had 699 names on it as of Monday night.

That number has fluctuated dramatically in the past week as additional people were reported missing or as some initially listed as unaccounted for either turn up alive or are identified among the dead.

Sheriff Kory Honea has said some people have been added to the list more than once at times under different spellings of their names.

As of early Tuesday, the fire had torched more than 61,100 hectares of parched scrub and trees and incinerated about 12,000 homes, Cal Fire said.

Efforts to suppress the flames were likely to benefit from a storm expected to dump as much as 10cm of rain north of San Francisco between late Tuesday and Friday.

Containment lines have been built around 70 per cent of its perimeter, according to Cal Fire.

Smoke from the fire has led to school closures in the region. Citing poor air quality, schools and colleges in the Sacramento area will remain closed until November 26.

Flights in and out of San Francisco also have continued to experience some delays or cancellations because of the smoke.

But heavy showers risk setting off mudslides in newly burned areas while also making it more difficult for forensic teams sifting through cinders and debris for additional human remains.

Australian Associated Press