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 areas in Los Angeles County, prompting evacuations and shutting down major roads.

Emergency responders have performed several rescues, including rescuing individuals trapped in vehicles as floodwaters rise. California's Governor Gavin Newsom declared a state of emergency on Wednesday for Los Angeles and other southern California counties.

As of Thursday evening, about 100,000 residents across the state were without power.

Moreover, numerous flash flooding events were anticipated, with warnings issued for many areas, including parts of the San Francisco Bay area.

A 64-year-old man from San Diego died when a fallen tree struck him, while a 74-year-old perished during a police rescue attempt from floodwaters in Redding. A woman in her 70s was killed by a large wave at MacKerricher State Park.

In Altadena, near Los Angeles, mudslides occurred in areas affected by wildfires, complicating emergency responses. Los Angeles Mayor Karen Bass has urged residents to stay safe and cautious, especially during this busy holiday travel season.

These storms, derived from multiple atmospheric rivers, have struck during one of the year's peak travel times, causing significant disruptions and safety concerns.