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.

The National Weather Service extended a Flash Flood Warning for parts of Southern California as the region gets hit with several inches of rainfall and strong winds.

A powerful storm carrying a strong atmospheric river is laying siege to California, where evacuations have been issued because of the risk of life-threatening flooding and debris flows.

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

Governor Gavin Newsom has declared a state of emergency in several California counties, including San Diego, due to heavy storms that have increased the risk of flooding and landslides, and has pre-deployed emergency response resources across the state.

State Fire & Rescue Chief Brian Marshall joins FOX Weather to discuss the latest updates for the ongoing flood threat throughout parts of California, as millions of people face continuous rain.