Officials cautioned that ash in recent burn zones was a toxic mix of incinerated cars, electronics, batteries, building materials, paints, furniture and other household items.

Less than an inch of rain fell in most areas, but it was enough to loosen Los Angeles hillsides charred by the blaze near the Pacific Palisades, where crews working before dawn cleared inundated roadways.

With parts of Los Angeles County still smoldering from wildfires, the expected rain this weekend would seem like a welcome relief. But how the rain falls could make the difference between a disaster respite or a disaster repeat.