Just over a month after thousands fled their homes as California saw the most destructive wildfires in its history, communities across the south of the state have now been hit by flash flooding and mudslides.
As the region is hit by what has been described as its largest storm of the season, pictures have emerged of cars being swept away in mudslides following heavy rainfall.
Authorities urged people to evacuate Felton Grove, a small community along the central coast, as the San Lorenzo River threatened to break its banks.
Southern California could get as much as six inches (about 15cm) of rain in the mountains and three inches (nearly 8cm) in coastal areas and valleys before the system moves out on Friday, said Brent Bower, a weather service hydrologist.
Powerful gusts have also threatened to bring down trees, cause power outages and delay flights.
In Altadena, mud flowed down a road during a flash flood in front of a bulldozer clearing debris in the Eaton Fire zone, while in the Pacific Palisades images showed a police officer stood at a junction in ankle-high flood waters.
Both areas were badly hit by the deadly wildfires last month as more than 18,000 structures were damaged or destroyed in the Eaton and Palisades blazes.
In the Hollywood Hills, a large debris flow left about eight inches (about 20cm) of mud across a road.
A swift flow of debris saw a Los Angeles Fire Department vehicle being swept off the Pacific Coast Highway and into the ocean in Malibu on Thursday.
One member of the fire department was in the vehicle and was able to exit with minor injuries, department spokesman Erik Scott said on X.
In Pacific Palisades, one of the affected areas in last month’s wildfires, one intersection of the highway was submerged in at least three feet of sludge.
Some drivers tried to force their way through and police officers pushed one vehicle through the mud.
In the San Francisco Bay Area, there were blackouts and small landslides.
To the north in wine country, concerns were high along the flood-prone Russian River.
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In Altadena, where a road in the north was also submerged by three feet of mud, vegetation and trees, Mehran Daoudian prepared by laying a sheet over a hole in his home’s roof where fire had burned through it last month.
Mr Daoudian said he was grateful city workers had arranged sandbags and concrete barriers in his neighbourhood.
“I did not leave the cars on the street because with the mudslide, (they) might go down,” he said.