Videos have been posted online of mudslides causing chaos in Southern California after a powerful rainstorm hit the area on Thursday. The storm has impacted a widespread swathe of Southern California with some mandatory evacuations being ordered over fears of rock slides and debris flows in recent burn scar areas,

With heavy rain bringing the risk of dangerous debris flows, the Los Angeles Fire Department has announced evacuation warnings — and mandatory evacuation orders for some specific addresses — in areas recently burned by wildfires.

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.