Photo: The Canadian Press

A helicopter drops water on a hill in the Oakmont area in Santa Rosa, Calif., Thursday.

They are trying to find lost loved ones, to sift through the remains of lost homes, to count, identify and mourn the dozens of dead — all while the fires rage on.

The communities of Northern California were preparing for another day under siege Friday, despite being driven to exhaustion by evacuations, destruction and danger amid the deadliest week of wildfires the state has ever seen.

"It wears you out," said winemaker Kristin Belair, who was driving back from Lake Tahoe to her as-yet-unburnt home in Napa. "Anybody who's been in a natural disaster can tell you that it goes on and on. I think you just kind of do hour by hour almost."

The death toll had climbed to an unprecedented 31, and was expected to keep rising. Individual fires including the Oakland Hills blaze of 1991 had killed more people than any one of the current fires, but no collection of simultaneous fires in California had ever led to so many deaths, authorities said.

"We had series of statewide fires in 2003, 2007, 2008 that didn't have anything close to this death count," said Daniel Berlant, a deputy director with the California Department of Forestry and Fire Protection.

Hundreds more were injured or missing.

Real recovery would have to wait for firefighters to bring under control the 21 wildfires spanning more than 300 square miles (777 square kilometres). Most were less than 10 per cent contained. New evacuations were still being ordered for fires that broke out on Sunday night.

"We are not even close to being out of this emergency," said Mark Ghilarducci, director of the state's Office of Emergency Services.

Choking smoke hung thick in the fire counties and drifted all over the San Francisco Bay Area, where masks to filter the fumes were becoming a regular uniform and the sunsets were blood-red from the haze.

"It's acrid now," said Wayne Petersen in Sonoma. "I'm wearing the mask because I've been here two or three days now, I live here, said Wayne Petersen in Sonoma. "It's starting to really affect my breathing and lungs so I'm wearing the mask. It's helping."

Authorities have brought tents and sleeping bags and opened public buildings and restaurants to house people seeking refuge in the safety and clean air of the coastal community of Bodega Bay.