In Santa Barbara, people living in at-risk areas were told to leave by 3 p.m. Wednesday. The National Weather Service in Los Angeles said on X around 5 p.m. local time that the storm was "rapidly intensifying" over Los Angeles County.

The National Weather Service warned that rain and flooding would intensify throughout the evening until around 10 p.m., bringing the risk of major flooding, debris flows and damaging winds.

Areas charred by last month's wildfires in Southern California now face a new threat from a powerful, but fast-moving Pacific storm. Here's what you need to know about this threat.