The second in a string of powerful storms battered Southern California on Saturday, shutting key highways after water and mud rushed into lanes from bare hillsides in wildfire burn areas where thousands of residents were under evacuation orders.

Flash flood warnings were issued for huge swaths of Southern California and forecasters said the system brought more than 4 inches (10 centimeters) of rain at lower elevations and several feet of snow in the mountains, where whiteout conditions closed roads.

A wind gust in Santa Barbara County topped 80 mph (128 kph) as the storm moved south and at one point dropped more than a half-inch (1.27 centimeters) of rain in five minutes. Trees and power lines were down across the region.

In Malibu, where the Woolsey fire last year destroyed homes and burned hillsides bare, officials closed Pacific Coast Highway and many other roadways after mud carried trees and rocks into lanes. Residents whose homes survived the flames barricaded their properties with sandbags to protect their properties from floodwaters.

Carol Cavella was evacuated during the November fire and again Saturday when the creek behind her house threatened to overflow and inundate her backyard.

The 86-year-old put her cat in the car and drove to a coffee shop on higher ground, her son-in-law, Warren Bowman said.

“She does not scare easily, but she got a little scared watching that water rise,” Bowman said. He was trying to convince her to come to his house in Los Angeles but she said she’d rather wait to see if the waters recede and she can return home.

The California Department of Transportation said Saturday night in a tweet that the both the northbound southbound lanes of U.S. 101, a vital route between Los Angeles and points north and west, have been reopened. Earlier Saturday, in the Montecito area of Santa Barbara County, several miles of U.S 101 were closed because of flooding.

Elsewhere in the county, evacuations were ordered or recommended for neighborhoods near the Thomas, Whittier and Sherpa fire scars.

“This is a dangerous situation,” the National Weather Service said, warning that the high rates of rain could send boulders sluicing down denuded hillsides along with the mud and debris.

It has only been a little over a year since a downpour on the huge Thomas Fire burn scar unleashed a massive debris flow that destroyed or damaged hundreds of homes in the seaside community of Montecito. The disaster killed 21 people, and two others have never been found.

Rescue crews scrambled Saturday to pluck motorists from cars caught in rising waters, said Mike Eliason, a spokesman for the Santa Barbara County Fire Department. He urged drivers who come upon flooded intersections to find alternate routes.