FRESNO, Sept 12 — US officials warned yesterday of potential "mass” fatalities as more than 20,000 firefighters from across the country battled sprawling deadly wildfires up and down the West Coast.

A prediction of cooler weather offered some hope of respite in coming days, but the true scale of the destruction from dozens of massive blazes in California, Oregon and Washington states remained hard to gauge.

There were 16 deaths confirmed this week, with wide stretches of land still cut off by flames.

"We’re preparing for a mass fatality incident based on what we know and the number of structures that have been lost,” warned Andrew Phelps, director of the office of emergency management in Oregon yesterday.

Oregon defines "mass fatality incident” as one that causes death and suffering which cannot be met by usual individual or community resources, according to the Washington Post.

"We anticipate that number (of deaths) may potentially go up as we get back into areas that have been ravaged by flame and obviously, smoke begins to clear,” warned California governor Gavin Newsom, as he visited a scorched forest near the raging North Complex Fire.

Ten people have been confirmed dead from that blaze in Butte County, which was driven at unprecedented pace toward the city of Oroville earlier in the week by strong, dry winds and soaring temperatures.

But Newsom said the weather "is beginning to cooperate,” with winds settling down and some rain forecast.

In neighbouring Oregon, where one million acres (400,000 hectares) have burned and three people are reported dead with dozens still unaccounted for, governor Kate Brown also expressed hope a corner had been turned.

More than 40,000 Oregonians have fled their homes so far, with around half a million under evacuation warnings, Brown told a press conference — clarifying previous higher figures given by state officials.

"The weather system fueling these fires over the past few days has finally broken down,” she said.

"We anticipate cooler air and moisture coming in the next few days, which is really good news.”

Dozens of people remained missing in connection with the fires, Brown said.

Even as the weather forecast offered hope, Newsom painted a grim picture of California as the canary in the climate-change coal mine.

"I’m a little bit exhausted that we have to continue to debate this issue,” he said in televised comments as he toured the damage. "This is a climate damn emergency. This is real, and it’s happening.

"This is the perfect storm.”

He added: "California, folks, is America fast-forward. What we’re experiencing right here is coming to communities all across the United States of America unless we get our act together on climate change, unless we disabuse ourselves of all the BS that’s been spewed by a very small group of people.”

‘Complete loss’

The August Complex Fire this week became by far the biggest recorded blaze in Californian history, ripping through 746,000 acres of dry vegetation in the state’s north, as multiple fires combined.

But it is just one of around 100 large fires on the West Coast, and other rapidly growing blazes closer to populated areas have proven deadlier.

"We are at a complete loss for words right now,” Bobbie Zedaker told the San Francisco Chronicle, after DNA tests proved her missing 16-year-old nephew was among those killed by the North Complex Fire.

Two more people were killed near the rural community of Happy Camp, a Cal Fire spokeswoman told AFP yesterday.

But in a mountainous region of central California, close to where the Creek Fire is burning, some members of an indigenous community refused to leave their homes despite evacuation orders.

"I don’t feel it’s going to come this way,” said James Hancock, 52, whose home on the Cold Springs Rancheria Indian Reservation currently has no light, electricity or water.

Huge wildfires are becoming more common, with the World Meteorological Organisation saying the five years to 2019 was unprecedented for fires, especially in Europe and North America.

Climate change amplifies droughts which dry out regions, creating ideal conditions for wildfires to spread out of control and inflict huge material and environmental damage.

California has already seen more than 3.1 million acres burn this year — an annual record, approximately the size of Connecticut — with nearly four months of fire season still to come. — AFP