California storm updates: 'This storm continues … take precautions,' mayor warns

The National Weather Service has a flood watch in effect Monday morning for some 40 million residents in California, where more than a month's worth of rain has fallen in the past 24 hours.

There was also a flash flood warning in effect until at least 9 a.m. PT for more than 4 million residents in Southern California, from the Santa Monica Mountains to the Hollywood Hills and Griffith Park, including the areas of Hollywood, Malibu, Beverly Hills, Burbank, Santa Monica, Encino and Brentwood. There were reports of numerous damaging landslides, inundated roadways, submerged vehicles as well as flooded creeks and streams within the region.

Automated rain gauges indicate between 5 and 8 inches of rain have already accumulated in the warning area, with rainfall continuing. An additional 1 to 4 inches of rain was possible there.

-ABC News' Kenton Gewecke and Morgan Winsor

Power is out for hundreds of thousands of electric customers in California amid severe weather.

As of 2:40 a.m. PT on Monday, more than 634,000 customers were without power across the Golden State, according to data collected by PowerOutage.us.

-ABC News’ Morgan Winsor

A man was killed by a falling redwood tree in his backyard in Yuba City in Northern California on Sunday, authorities said.

The Yuba City Police Department identified the victim as 82-year-old David Gomes.

A neighbor, who reported the incident, told the responding officers that they last saw Gomes at around 3 p.m. PT and believed they heard the tree fall about two hours later, according to police.

“Through the investigation, it appeared Gomes was possibly using a ladder to try and clear the tree away from his residence when it fell on him,” police said in a statement.

-ABC News’ Marilyn Heck and Morgan Winsor