Rain fell on parts of Southern California on Sunday and the scattered showers were expected to continue overnight, boosting the risk of toxic ash runoff in areas scorched by Los Angeles-area wildfires.

LOS ANGELES — Rain began falling in parched Southern California on Saturday in a boon for firefighters who were mopping up multiple wildfires. But heavy downpours on charred hillsides could bring the threat of new troubles like toxic ash runoff.

In the aftermath of the Southern California wildfires, health experts are warning residents about the possible dangers of toxins still lingering in the air. Ash, smoke and other chemicals can easily seep into homes and buildings,