Much-need rain has begun to fall over Southern California, bringing relief to the drought-stricken region but also the threat of toxic runoff.

A major rainstorm sweeping through the Los Angeles area is threatening Southern California's recovery from this month's devastating wildfires, creating dangerous conditions that could include debris flows and mudslides.

High rain over a burn scar may result in debris flows or mudslides. Follow the instructions of local officials!” the National Weather Service said.

Rain on land burned by a series of devastating fires in the Los Angeles area has the potential to contribute to flooding and debris flows.