Ahead of the storm’s arrival, officials in Southern California distributed sandbags, prepositioned rescue swimmers and told residents to have go-bags ready.

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.

Most of the California coast is under a flood alert as torrential rain and mountain snow intensified over California Thursday morning, part of yet another atmospheric river storm, bringing a significant risk of flooding and landslides in areas recently affected by devastating wildfires.