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.

The National Weather Service issued a warning of a “particularly dangerous situation” for parts of Los Angeles and Ventura counties from Monday afternoon through Tuesday morning.

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.