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.

Weekend rains could bring some relief to Southern California. Here's the forecast and an assessment of how much it will help reduce fire risk.

A wet pattern will bring periods of rain and showers to Southern California, dropping an inch or two in the Los Angeles region — the most to fall since mid-April. It will be key for firefighters continuing to battle flames.