The first significant storm of the season has brought snow and downpours to Southern California that doused wildfires and caused some ash and mud to flow across streets in the Los Angeles area.

Rain falling on Southern California is expected to aid firefighters mopping up multiple wildfires. But potentially heavy downpours on charred hillsides could bring new troubles such as toxic ash runoff.

Less than an inch of rain fell in most areas, but it was enough to loosen Los Angeles hillsides burned bare by the recent blaze near the Pacific Palisades.

More rain fell Monday on parts of Southern California after causing mudflows over the weekend, helping firefighters but boosting the risk of toxic ash runoff in areas scorched by Los Angeles-area wildfires.

Southern California’s first significant storm of the season brought weekend downpours that aided firefighters but caused ash, mud and debris to flow across streets in wildfire-burned areas.