More than 41 million Americans across California, southern Nevada and northwest Arizona are under flood watches on Wednesday amid a rare, high risk for excessive rainfall and flooding. This includes major metros like Los Angeles,

Another round of storms is moving across California this week, bringing periods of heavy rain, strong winds and flooding concerns.

A powerful winter storm swept across California on Wednesday, with heavy rain and gusty winds leading to evacuation warnings for mudslides in the south, bringing near white-out snow conditions in the mountains and hazardous travel for millions of holiday drivers.

Forecasters said Southern California could see its wettest Christmas in years and warned about flash flooding and mudslides.

On Wednesday at 3:05 a.m. the NWS San Francisco CA released an updated severe thunderstorm warning in effect until 3:15 a.m. The warning is for San Mateo, Santa Clara and Santa Cruz counties.

As severe thunderstorms roll across California, the possibility of funnel clouds or a tornado can't be ruled out. A portion of the Central Valley is under a marginal thunderstorm threat, according to the Storm Prediction Center.

Heavy rain from a persistent atmospheric river pattern continues to impact California this week. Here's what's causing it.

The National Weather Service (NWS) issued "life-threatening" flash flood warnings for parts of Southern California. Follow Newsweek live.