California reports multiple fatalities from ongoing wildfire

At least four people are now known to have died in a wildfire sweeping through California, authorities said, as they warned the toll from the western US state's worst blaze this year could rise further.

"We have four fatalities confirmed, and that number could change," Siskiyou County Sheriff's Department spokesperson Courtney Kreider told the AFP news agency on Tuesday.

Two of the dead were found in a car on Sunday, apparently caught in the flames as they tried to flee.

There were no details about the other deaths.

At least 3,000 people have been told to leave their homes in and around the town of Klamath River, with 100 structures already destroyed.

"Our goal today is to effectively communicate with people, and we're asking them to obey the evacuation orders," Kreider said.

"Our priority is to protect life and property."

Rain and cooler conditions brought some relief to hundreds of firefighters battling to protect the 8,000-person town of Yreka, but the human cost of the inferno was already mounting.

READ MORE: California: Largest blaze of the year claims lives as thousands evacuate

Unstable fire behaviour 

State fire department CalFire said better weather overnight had helped limit the spread of the so-called McKinney Fire, but vegetation remained extremely dry and vulnerable to lightning strikes.

"The continued threat of thunderstorms and the associated strong, erratic winds could result in increased fire behaviour," CalFire said.

The fire, which is burning in the Klamath National Forest near the border with Oregon, is California's largest this year, having consumed around 56,000 acres.

Firefighters were working to contain its spread, using bulldozers to create firebreaks around Yreka.

They were also battling spot fires, which erupt as sparks shoot off from the main blaze and ignite some distance away.

READ MORE: Wildfires in western US explode in size amid windy conditions

Man-made crisis

The drought, exacerbated by the man-made climate crisis, has left the countryside parched and vulnerable to naturally occurring wildfires, making the blazes hotter, faster and more destructive.

Dennis Burns, a fire behaviour analyst with the California Interagency Incident Management Team, said there was a potential for thunderstorms and heavy downpours on Tuesday that could give firefighters the edge they were looking for.

"We're not expecting any significant movement of the fire but we could still see active flaming," he said.

California still has months of fire season ahead of it.

Other parts of the world have also faced intense wildfires this year, as scientists say climate crisis and global heating is making heatwaves more frequent and more intense, increasing the risk of fires.

READ MORE: Thousands evacuated as 'explosive' California wildfire widens