Powerful gusts have pushed flames from a wildfire through Southern California canyons.
One of several blazes that burned near homes has forced residents to flee and prompted utilities to cut off power to hundreds of thousands.
The biggest blaze began late on Wednesday as a house fire in Orange County’s Silverado Canyon, where gusts topped 115km/h.
The fire grew to more than 30 square kilometres and blanketed a wide area with smoke and ash.
Crews struggled in steep terrain on Thursday amid unpredictable Santa Ana winds that sent flames racing across major roads.
Two firefighters were hospitalised after being treated on scene for injuries. Their condition was not immediately known.
Some homes were damaged in the fire and possibly destroyed.
Evacuations were ordered for thousands of residents of canyon and foothill neighbourhoods near the city of Lake Forest and residents of other nearby areas were told to be ready to get out.
There was no containment of the fire.
The Bond Fire about 80km southeast of Los Angeles is burning near the same area of October’s Silverado Fire, which forced tens of thousands of people to evacuate.
Utilities in the populous region began cutting power Wednesday to customers as a precaution to prevent gusts from blowing tree limbs into electrical equipment or knocking down power lines, which have sparked devastating wildfires in recent years.
And to the south, a small blaze in San Diego County threatened about 200 homes and prompted evacuations before firefighters managed to contain 50 per cent of it. At least one structure was destroyed and six others were damaged.
California already has experienced its worst-ever year for wildfires.
More than 16,800 square kilometres have been scorched.
At least 31 people have been killed and 10,500 homes and other structures damaged or destroyed.
The latest fire threat comes as much of California plunges deeper into drought.
Virtually all of Northern California is in severe or extreme drought while nearly all of Southern California is abnormally dry or worse.