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 are expected to continue through Friday - brought 11 inches (27 cms) of rainfall to some parts of Los Angeles County, prompting evacuations and shutting down major roads.
Emergency responders have had to perform several rescues, including people stuck in vehicles as flood waters rose. 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 numerous flash flooding events are possible, adding that many streams may flood, potentially affecting larger rivers.
A 64-year-old man from San Diego, California, was killed on Wednesday morning by a fallen tree. Another person, a 74-year-old, died from flood waters over the weekend as police tried to rescue him from a vehicle in Redding, California. On Monday, a woman in her 70s died after being knocked off a rock by a large wave and swept into the ocean at MacKerricher State Park in Mendocino County.
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 on Thursday morning. Wind speeds in the Bay Area topped 100 mph (161 km/h) at one observatory near San Jose.
In Altadena, near Los Angeles, residents experienced a mudslide from flooding in a burn scar area that was less able to absorb water due to the wildfires that scorched the neighborhood earlier this year. Los Angeles Mayor Karen Bass has also declared an emergency from the storms and warned residents to be cautious on roads during this busy holiday travel time.
The storms brought multiple atmospheric rivers from the tropics during a critical period of travel ahead of the holidays.
