A powerful Christmas week storm is dumping rain across Southern California, putting at-risk communities on alert and prompting evacuation warnings.

Three people are dead after major storms swept through California, dumping rain and leaving behind catastrophic flooding during the Christmas holiday — and even more rain is in the forecast.

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

A flood watch remained for the Bay Area after the National Weather Service issued a flash flood warning overnight until 6 a.m.

Millions of people in the Northeast are under winter storm warnings for a threat of snow and ice expected to hit the region Friday into early Saturday.

Temperatures will hover in the mid to upper 20s as precipitation begins, creating hazardous travel conditions.

Several days of rain and powerful wind gusts are in the forecast this week when a winter storm has already led to evacuation warnings in parts of Los Angeles County settles into Southern California for the holiday.

An emphasis has been placed on burn scar areas that are more susceptible to flooding, mudslides and debris flows.