Fast-moving wildfires near Los Angeles have caused at least one death, forced the evacuations of thousands of homes and triggered widespread power outages.
Some 27,000 residents were forced to flee their homes in the middle of the night as a wind-fueled fire ripped through southern California.
Several thousand homes are under mandatory evacuation in the cities of Ventura and Santa Paula, 115km north of Los Angeles.
Fanned by high winds, the fire swept through 12,500ha in a matter of hours.
Officials said one person died in a traffic accident while trying to flee the blaze and one firefighter was injured.
#ThomasFire is now 26,000 acres with 0% perimeter containment. Fire & Sheriff resources continue with impact area evacuations and structure protection operations. @VCFD #VCFD pic.twitter.com/qbdOJwPzBu— VCFD PIO (@VCFD_PIO) December 5, 2017
Officials said the blaze, known as the Thomas Fire, destroyed 150 buildings and left more than 260,000 people without power.
About 500 firefighters battled the blaze but fire chiefs admitted they were fighting a losing battle.
"The prospects for containment are not good. Really, Mother Nature is going to decide," Ventura County Fire Chief Mark Lorenzen told reporters.
Strong eastern winds pushed the fire toward the cities of Santa Paula and Ventura, where about 140,000 people live, county officials said.
Residents received mandatory evacuation notices via their phones and from emergency workers going house to house.
"My son is a firefighter and I'm not going to wait around for someone to rescue me," June Byrum told CBS, saying her 91-year-old father, husband and dog had already left for a safe place.
A second fire overnight, known as the Creek Fire, consumed at least 2500 acres in the foothills of Angeles National Forest north, forcing residents of some nearby San Fernando Valley communities north of Los Angeles to flee, the Los Angeles County Fire Department said.
The Thomas Fire was stoked by Santa Ana wind gusts blowing out of the desert to the east that were expected reach 115 km/h hour and remain strong through the week as well as by low humidity.
About 390 students at Thomas Aquinas College were evacuated as a precaution, the school said on Twitter. Evacuation centres were opened at a high school and the county fairgrounds, media reported.
California has been hit hard by wildfires in recent months.
At least 40 people were killed when fires ripped through parts of northern California's wine region in October. Some 10,000 structures were destroyed.
- BBC / Reuters