A new wildfire that broke out north of Los Angeles has rapidly spread to more than 9,400 acres, or 38sq/km, fueled by strong winds and dry brush, and forcing mandatory evacuation orders for more than 31,000 people.
The Hughes fire, about 80km north of Los Angeles, further taxed firefighters in the region who have managed to bring two major fires in the metropolitan area largely under control.
In just a few hours, the new fire grew to two-thirds the size of the Eaton Fire, one of the two conflagrations that have ravaged the Los Angeles area.
Officials warned people in the Castaic Lake area of Los Angeles County that they faced "immediate threat to life," while much of southern California remained under a red-flag warning for extreme fire risk due to strong, dry winds.
Some 31,000 people were under mandatory evacuation orders and another 23,000 face evacuation warnings, Los Angeles County Sheriff Robert Luna told a press conference.
The Angeles National Forest said its entire 2,800sq/km park in the San Gabriel Mountains was closed to visitors.
As a result of the red-flag warning, some 1,100 firefighters were deployed around southern California in anticipation of fast-moving fires, the California Department of Forestry and Fire Protection said.
More than 4,000 firefighters were working on the Hughes Fire, Los Angeles County Fire Chief Anthony Marrone said.
Southern California has gone without significant rain for nine months, contributing to hazardous conditions, but some rain was forecast from Saturday through Monday, possibly giving firefighters much-needed relief.
Helicopters scooped water out of a lake to drop on the fire while fixed-wing aircraft dropped fire retardant on the hills, video on KTLA television showed.
Flames spread to the water's edge.
Interstate 5, the major north-south highway in the western United States, was temporarily closed in the mountain pass areas known as the Grapevine due to poor visibility from the smoke, the California Highway Patrol said.
But firefighters were able to suppress enough of the fire to reopen the highway, Mr Marrone said.
While the new fire raged, the two deadly fires that have ravaged Los Angeles since 7 January came under greater control, CalFire said.
The Eaton Fire that scorched 57sq/km east of Los Angeles was 91% contained, while the larger Palisades Fire, which has consumed 95sq/km on the westside of Los Angeles, stood at 68% contained.
Containment measures the percentage of a fire's perimeter that firefighters have under control.
Since the two fires broke out on 7 January, they have burned an area nearly the size of Washington DC, killed 28 people and damaged or destroyed nearly 16,000 structures, Cal Fire said.
Around 180,000 people were under evacuation orders, according to Los Angeles County officials.
Private forecaster AccuWeather projects damage and economic losses at more than $250 billion.
A series of smaller wildfires has been extinguished or brought largely under control in Southern California the past two weeks.
