Much of southwestern California is under a flood advisory as rain makes travel dangerous, while a snowstorm heads for the Northeastern U.S.

Days into an atmospheric river event that has deluged the state since the weekend, officials warned of heavy rains and flood risks in Southern California.

A powerful storm brought heavy rain to parts of California on Wednesday, flooding roads and prompting evacuations in some areas. The deluge of rain is causing dangerous travel conditions on Christmas Day.

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

Firefighters were also going door to door to check on residents, and the area was under a shelter-in-place order, local officials said.

The Christmas Eve drive was anything but a holiday gift for many across Los Angeles as heavy rain turned roads into rivers in some areas. At LAX, the last-minute dash to make it home before Christmas had flyers lining up early hoping the storm didn't keep them grounded.

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 a "very dangerous" holiday storm could trigger "widespread flash flooding."