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

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.

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.

Torrential rains drenched Southern California on Wednesday, unleashing widespread flash flooding as authorities urged motorists to stay off roads and residents living downslope of wildfire-scarred foothills and canyons to evacuate.

A man was found dead in what appeared to be a weather-related incident in Lancaster, according to the Los Angeles County Sheriff's Department.

The Red Cross is also offering additional services to those whose homes have been damaged. However, volunteers must first assess the damage to determine eligibility for assistance.