Severe hot and dry "devil winds" have kicked up in fire-ravaged southern California and more winds are expected in the state's north, fanning the flames of wildfires that have killed at least 25 people.
"This is getting bad," said meteorologist Marc Chenard from the National Weather Service's Weather Prediction Centre.
Chenard said sustained winds of up to 65 kilometres per hour and gusts between 100 and 110km/h were expected in the Los Angeles area.
There, a blaze known as the Woolsey Fire has been burning since Thursday in the tinder-dry canyon of Ventura County, and has claimed at least two lives.
The air masses blowing across the western US deserts, including Death Valley, toward the coast are expected to bring the sustained high winds at least through Tuesday, Chenard said.
"It's nothing but bad news," he said.
Additional 65km/h winds will blow across the Sierra Nevada foothills in northern California near Sacramento, where the so-called Camp Fire has claimed at least 23 lives.
The Camp Fire burned down more than 6700 homes and businesses in the town of Paradise, more structures than any other California wildfire on record.
The blaze is also one of the state's deadliest; only the Griffith Park Fire in 1933 and the Tunnel Fire in 1991 have claimed more lives.
Several of the bodies discovered earlier this week were found in or near burned out cars, police have said.
The flames descended on Paradise so fast that many people were forced to abandon their vehicles and run for their lives down the sole road through the mountain town.
An additional 35 people have been reported missing and three firefighters have been injured.
It was not immediately clear if any of the missing were among those found dead.
As of Saturday night, the Camp Fire had blackened more than 40,500 hectares at the edge of the Plumas National Forest.
About 800km to the south, the Woolsey Fire burning in the foothills above Malibu doubled in size from Friday night into Sunday.
The blaze threatened thousands of homes after triggering mandatory evacuation orders for a quarter of a million people in the upscale beach city, as well as other communities in Los Angeles and Ventura counties.
The fire has destroyed at least 177 homes and other structures with a full count still under way, and has charred more than 33,600ha as of late Saturday, officials said.
US President Donald Trump weighed in on the emergency during a trip to France for Armistice commemorations.
"With proper Forest Management, we can stop the devastation constantly going on in California. Get Smart!" he tweeted early on Sunday.
Trump has previously blamed California officials for fires and threatened to withhold funding, saying the state should do more to remove rotten trees and other debris that fuel blazes.
State officials have blamed climate change and say many of the burn areas have been in federally-managed lands.