Evacuations in California after 'fire on all sides'

More than 200 people have been airlifted to safety overnight after a fast-moving wildfire cut off the only road out of the Mammoth Pool Reservoir, a popular recreational site in California's Sierra National Forest.

Twenty evacuees were taken to hospitals, the Madera County Sheriff's Department said on Twitter on Sunday, as the Creek Fire that started on Friday night rapidly grew to burn some 18,210 hectares or 182 square kilometres, forcing evacuations and road closures in the Fresno area in central California.

"We're completely trapped. There’s fire on all sides, all around us," said Jeremy Remington, as he stood on a beach surrounded by fire in the Mammoth Pool Reservoir in a video posted on Twitter. Remington was later airlifted to safety, local news reported.

The blaze was 0% contained on Sunday afternoon, while nearly 15,000 firefighters were battling some two dozen fires across the state, according to the California Department of Forestry and Fire Protection (CalFire).

Eight people have been killed and some 3,300 structures have been destroyed over the past three weeks in wildfires across the state.

Three major fires, including the Creek Fire, were burning in Fresno, San Bernardino and San Diego counties, the agency said in a statement, adding it had increased staffing in preparation for "critical fire weather."

The San Diego County Sheriff's Department issued a voluntary evacuation order on Sunday afternoon as the 5,350-square acre Valley Fire raged unchecked on the eastern edge of the metropolitan area of more than 3 million people.

"The sky is so thick by my house; the sky is a dirty brown cloud and I live about 25 minutes to the west of the fire," Twitter user Cris Mel said in a post. "It’s kind of a struggle to breathe."

A dangerous heat wave was baking swaths of the western United States through the weekend, and many locations in California registered record-high temperatures on Sunday.

The temperature reached 49 C (121 degrees F) on Sunday afternoon in Los Angeles County, a record for the National Weather Service office that covers the metropolitan area.

"This is a historic heat wave for southwestern CA and one that will be remembered for a long time," the service said in a statement.

State officials on Sunday repeated calls to Californians to turn off appliances and lights to help avoid blackouts from an overwhelmed power grid.

Southern California Edison Co (SCE), which services 5 million customer accounts in the region, was advising customers of potential rotating outages between 4 p.m. and 9 p.m. on Sunday.

Rotating outages — in which utilities purposely cut power temporarily to avoid broader outages — are rare. They last occurred in the region in August. Before that, they had not occurred in 20 years, said SCE spokesmen Reggie Kumar.