Nearly 20 major fires have ravaged the sprawling western state over the past two weeks, fanned by strong winds and sweltering temperatures.
The wildfires have left at least nine people dead, including four firefighters, and forced tens of thousands of residents to abandon their homes.
"It's scary, it's nerve-wracking," said Jay Michael, who was resting in a van in a parking lot in Clearlake Oaks with Gretchen Fritsch after fleeing their home.
"I got a feeling my home's still there," Michael told AFP. "My gut's telling me it's still there but..."
He said it was the eighth time they have evacuated since living in the area north of San Francisco, and the third time this year.
The National Weather Service said conditions were expected to remain very hot and windy until at least Saturday evening.
While no respite was expected from the weather, authorities said the 14,000 firefighters battling the blazes have made progress against the Mendocino Complex Fire comprising twin blazes in the state's north -- the River Fire and the Ranch Fire.
The Mendocino Complex Fire has swept through over 300,000 acres (120,000 hectares) -- approximately the size of Los Angeles -- and is California's largest wildfire since record-keeping began a century ago.
|An air tanker drops retardant on the Ranch Fire, part of the Mendocino Complex Fire, burning along High Valley Rd near Clearlake Oaks, California, Aug. 5. (AFP)|
The River Fire is 81 percent contained, having burned 48,920 acres, Cal Fire said.
Its partner blaze, the Ranch Fire, has grown to 251,000 acres and is 46 percent contained.
- Fire sweeps over barriers -
Overall, the Mendocino Complex Fire has destroyed at least 221 structures, 116 of them residences, Cal Fire said. More than 10,000 other structures are threatened.
The Ranch Fire, which poses the biggest challenge, has swept across natural barriers like rivers, and a ditch dug with earth-moving machinery.
Helicopters and airplanes, including two massive DC-10s and a 747 jumbo jet, have supported firefighters by dousing the flames with water.
Besides firefighters from around the country and abroad, about 1,000 National Guard personnel are supporting wildfire operations in California, with another 450 in Oregon and 170 in Washington state.
The Carr Fire, near the town of Redding, has engulfed more than 173,000 acres since igniting July 23, killing seven people so far including two firefighters.
As of early Wednesday, firefighters had managed to get it 47 percent contained.
Another major fire, Ferguson, has left two people dead and forced the closure of part of Yosemite National Park. It is currently 43 percent contained.
In southern California near San Diego, hundreds of firefighters have been deployed to tackle the fast-moving Holy Fire in the Cleveland National Forest.
Cal Fire officials said a shift in the weather can make a big difference for firefighting crews.
"Weather was a big factor today and due to the winds aloft covering the fire area in smoke, it caused lower than predicted temperatures," Cal Fire said Tuesday evening.
"The temperature decrease allowed crews to continue valuable work to contain the fire perimeter edge, slowing fire growth," it added.
On Monday alone, 127 wildfires were burning on 1.6 million acres of land in 11 states, the National Interagency Fire Center said.
The Mendocino Complex Fire is the second blaze to break records in California in as many years, following the Thomas Fire in December 2017 that destroyed 281,893 acres.