Atmospheric rivers dumped heavy rains on large parts of California, causing floods and mudslides and leaving three dead as of Christmas night, according to local officials.
The storms - which were expected to continue through Friday - brought 11 inches (27 cms) of rainfall to some parts of Los Angeles County, prompted evacuations and shut down major roads.
Emergency responders have had to perform several rescues, including people stuck in vehicles as flood waters rise. California's Governor Gavin Newsom declared a state of emergency on Wednesday in Los Angeles and other southern California counties.
About 100,000 people in the state were without power as of Thursday evening.
The US Weather Prediction Center said on Thursday that Numerous flash flooding events are possible and warned residents to stay alert. The storms caused devastation, including the death of a 64-year-old man in San Diego due to a fallen tree and several other fatalities linked to the rising waters.
Evacuation warnings were in effect for some residents of San Bernardino County in southern California, and flash flood warnings were issued for those in the San Francisco Bay area. Wind speeds in the Bay Area topped 100 mph (161 km/h) at one observatory near San Jose.
Los Angeles Mayor Karen Bass warned residents to be cautious on roads during this busy holiday travel time and characterized the storms as a serious threat to public safety. The storms stem from multiple atmospheric rivers carrying moisture from the tropics, hitting during one of the busiest travel weeks of the year.
