Torrential rains unleashed widespread flash flooding and mud flows across Southern California on Wednesday, as authorities warned motorists to stay off roads while urging residents in flood zones to evacuate or shelter in place.

Officials in Los Angeles and surrounding counties warned that the giant holiday storm could trigger "widespread flash flooding."

The National Weather Service (NWS) issued "life-threatening" flash flood warnings for parts of Southern California. Newsweek's live blog is closed.

Potentially catastrophic rain is heading toward Los Angeles -- a region already scarred by recent extreme weather and climate events, making it more vulnerable.

On Wednesday, Caltrans alerted drivers that a stretch of the 5 freeway, both north and southbound lanes near Lankershim Boulevard, closed due to flooding and mud. Just after 6 p.m., several southbound lanes reopened while generators continued pumping out water for hours.

The storms have moved out, but many across the Bay Area are in cleanup mode, after torrential rains led to flooding.