Five of the largest wildfires in state history are currently burning and more than 5,600 square miles have been charred, an area larger than the state of Connecticut, state governor Gavin Newsom said.
At 165 square miles, the so-called Bobcat Fire is one of the largest ever in Los Angeles County after burning for more than two weeks. It was only about 17% contained.
Evacuation orders and warnings are in place for thousands of residents in foothill and desert areas, where semi-rural homes and a popular nature sanctuary have burned. Statewide, at least 23,000 people remain evacuated, Mr Newsom said.
No injuries have been reported from the fire about 50 miles northeast of downtown Los Angeles.
However, 18 homes and other buildings have been destroyed and 11 damaged, some in the Juniper Hills area, with the toll rising to perhaps 85 when damage assessment teams can complete their work this week, fire officials said Monday evening.
Nearly 19,000 firefighters in California are currently battling 27 major blazes, Mr Newsom said. At least 7,900 wildfires have erupted in the state this year, many during a mid-August barrage of dry lightning ignited parched vegetation.
Twenty-six people have been killed. Officials were investigating the death of a firefighter at another Southern California wildfire that erupted earlier this month from a smoke-generating pyrotechnic device used by a couple to reveal their baby’s gender.
Erratic winds that drove flames into the state’s community of Juniper Hills over the weekend had died down, said US Forest Service spokesman Larry Smith.
“It’s slightly cooler too, so hopefully that will be a help to firefighters,” Mr Smith said.
However, evacuation warnings — meaning residents should be prepared to flee if ordered — remained in effect for Pasadena, home of the Rose Bowl and the annual Rose Parade, and Wrightwood, a mountain community near several ski resorts.
Numerous studies in recent years have linked larger US wildfires to global warming from the burning of coal, oil and gas, especially because climate change has made California much drier, meaning vegetation is more flammable.
Officials said it could be days before teams determined the scope of the destruction in the area burned by the Bobcat Fire.
Early estimates are that 6,400 buildings have been destroyed across the state, but Mr Newsom said “by no stretch of the imagination do we think this tells the entire story”.
The Bobcat Fire started on September 6 and has doubled in size over the past week while ripping through forested areas that had not burned in decades. The cause is under investigation.
Firefighters battled back against another flare-up near Mount Wilson, which overlooks greater Los Angeles in the San Gabriel Mountains and has a historic observatory founded more than a century ago and numerous broadcast antennas serving Southern California.
Flames destroyed the nature centre at Devil’s Punchbowl Natural Area, a geological attraction that draws some 130,000 visitors per year. A wildlife sanctuary on the property was undamaged, and staff and animals had been evacuated days earlier.
