More than 100 homes were under mandatory evacuation orders in the city of Los Angeles, Jim McDonnell, the Los Angeles police chief, said Thursday morning. The Palisades fire destroyed thousands of homes in the city’s Pacific Palisades neighborhood last month, and hillsides remain vulnerable in the area.

In the Los Angeles area, the burn scars that carry the highest risk are those from the Eaton and Palisades fires from January and the Bridge Fire from the fall.

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.