A swift debris flow swept a Los Angeles Fire Department vehicle off the Pacific Coast Highway and into the ocean in Malibu on Thursday as heavy rain fell across Southern California, creating deluges of water and mud on roads at the bottom of hillsides left barren by the recent wildfires.

As the heaviest rain storm of the winter season reached its peak on Thursday afternoon, some of Southern California’s most vulnerable areas braced for the potential impact. Crews and officials across the region prepared for potential mudslides,