Heavy rain storms across much of California have triggered catastrophic flooding and mudslides, leading to three confirmed fatalities by Christmas night, local officials report.

The storms, expected to persist until Friday, have resulted in over 11 inches (27 cm) of rainfall in some regions of Los Angeles County and have forced evacuations while major highways have been closed due to severe conditions.

Emergency responders have been actively performing rescues, including assisting individuals trapped in vehicles caught in rising flood waters. The governor of California, Gavin Newsom, declared a state of emergency on Wednesday impacting Los Angeles and surrounding southern counties.

By Thursday evening, roughly 100,000 residents in the state were without power. The U.S. Weather Prediction Center warned of the possibility of numerous flash floods, threatening creeks and even larger rivers.

Tragically, a 64-year-old resident from San Diego lost his life Wednesday morning after being crushed by a falling tree, while a 74-year-old man perished over the weekend due to flood waters, with rescue attempts underway when he was in his vehicle.

In Mendocino County, a woman in her 70s died on Monday after being swept into the ocean while visiting MacKerricher State Park. Evacuations have been initiated for certain areas in San Bernardino County, as flash flood warnings extend to the San Francisco Bay area.

Wind speeds reached over 100 mph (161 km/h) at an observatory near San Jose, according to reports. Flooding has exacerbated issues in Altadena, where a mudslide occurred in areas stripped of vegetation due to prior wildfires.

Los Angeles Mayor Karen Bass declared an emergency reflecting the severity of the storms and urged residents to prioritize safety while traveling during this busy holiday season.

The excessive rainfall was attributed to multiple atmospheric rivers, carrying moisture from the tropics, coinciding with one of the year's most hectic travel times.