Homes have been swept from their foundations and residents are being rescued as mud and debris from wildfire-scarred hillsides flows through neighbourhoods and on to a key southern California highway during a powerful winter storm.
Helicopters are being used to rescue residents as the storm drops record amounts of rain across the state because roads are blocked, Santa Barbara County spokeswoman Amber Anderson said.
"The primary issue right now is access. We’ve got trees and power lines down," she said.
There were reports of injuries, but Ms Anderson did not know how many or the extent.
She said "multiple" residents had been taken to safety and dozens more were calling for help in Montecito and Carpinteria.
Some of those rescued were buried in mud, officials said, and thousands were without power.
Crews worked to clear debris from roads across greater Los Angeles, including a key stretch of US 101 that was shut down along the border of Santa Barbara and Ventura counties.
Evacuation orders were issued on Monday as forecasters predicted mudslides in foothill neighbourhoods where the state’s largest-ever fire raged last month.
The first significant storm of the season hit much of the state with damaging wind and thunderstorms.
Record-breaking rain fell on the San Francisco Bay region before the system largely passed overnight, leaving diminishing showers before dawn.
Breaking: Two people are dead due to a powerful storm that unleashed flooding and mudslides in Santa Barbara County, fire officials say https://t.co/hmwH6BUi8F— NBC Los Angeles (@NBCLA) January 9, 2018
Stormy weather continued to the east in the Central Valley and Sierra Nevada.
Central San Francisco had 3.15in of rain, smashing the old mark of 2.36in set in 1872 and making it the city’s 16th wettest day since 1849, the National Weather Service said.
To the south, a staggering 9.6in of rain fell on Mining Ridge on the Big Sur coast.
Highway 1, still not recovered from last winter’s damaging rains, suffered new blockages.
Forecasters issued flash flood warnings and predicted that the cold front with powerful winds could bring more rain to central Los Angeles than recorded over the past 10 months.
Mandatory evacuations were ordered for about 700 homes in former burn areas of Los Angeles County.
A winter weather advisory was in place for mountain areas, where officials warned motorists to prepare for difficult travel conditions, including gusty winds, low visibility and snow-covered roads
A years-long drought eased in the state last spring, but northern California had a dry start to winter and hardly any measurable rain fell in the south over the past six months.
The extremely dry conditions and high winds last year led to some of the most destructive blazes at both ends of the state.