The biggest "Thomas" fire has charred nearly 95,000ha of land and is only 20 per cent contained, according to the state agency Calfire.
But in the past day or so, that figure has risen by only a thousand hectares. Evacuation orders were issued for threatened areas in the Santa Barbara region about 160km northwest of Los Angeles.
Nearly 6,400 firefighters have been toiling for a week against blazes fueled by bone dry conditions and powerful winds.
Winds will blow at up to 65km per hour, forecasters said, as public health authorities urged people to wear face masks to protect against ash and smoke.
’End of an era’
Retired pilot Don Thompson, who has an avocado farm in Carpinteria, near Santa Barbara, described the loss of his recently deceased brother’s house to the blaze as "the end of an era for our family."
"He built this house himself," he said pointing to two smoldering stone chimneys that were all that remained.
Half of his family’s avocado orchard was destroyed, while thick black smoke persisted on Tuesday, limiting visibility to some 50m.
"There was some tears," he continued. Though he was more fortunate to save his own property, thanks partly through his family’s own efforts with a water pump and hose, he had been overawed by the "majesty" of the inferno.
"It’s destruction but it’s still nature and it had some beauty," he said.
Another resident of the area, Ken Coffey, said he would remain at his house on Shepard Mesa Lane.
"I may fry but if I have to go, what more honorable way than defending your family’s house?"
"Thomas" is the fifth biggest fire in California’s history, said Eric Boldt, a meteorologist with the National Weather Service in Los Angeles.
It is the biggest of six blazes that have been burning since last Monday, with the others now more than 90 per cent contained.
Altogether, the fires have burned more than 100,000ha of land and forced the evacuation of hundreds of thousands of people.
California’s Governor Jerry Brown, meanwhile, warned the wildfires ravaging his state should serve as a warning for other parts of the world threatened by climate change.
"The important fact is that these fires are going to become a very frequent occurrence, that’s what the science is telling us," he said on the sidelines of the One Planet Summit, held in Paris.
"It’s a real indicator of bad things to come and hopefully will serve to wake up people who right now are too complacent," he added.
Experts say that global warming increases the risk of out-of-control blazes by drying out vegetation, making it more inflammable and easily set alight by lightning, spontaneous combustion, or fires lit by humans. Source from VNS