After weeks of windy and dry weather, rain has fallen in parched Southern California and is expected to aid firefighters who are mopping up multiple wildfires. But potentially heavy downpours on charred hillsides could bring new troubles such as toxic ash runoff.

Rain was falling across Southern California on Sunday, bringing some relief to thousands of firefighters who have been battling multiple major wildfires in the LA area.

Rainfall has provided relief to wildfire-stricken Southern California but posed new threats of toxic ash runoff and debris flows. Authorities are expediting cleanup efforts and implementing flood-control measures to mitigate environmental impacts.