Southern California is bracing for possible mudslides even as rain subsides

A ferocious atmospheric river storm that has been battering California for days began to weaken Tuesday, but officials warned that even small amounts of additional precipitation could trigger landslides in rain-soaked Southern California.

Between Sunday and Monday, the storm dumped record-breaking amounts of rain into the Los Angeles basin, forcing millions of residents to stay home to avoid potential hazards. By Monday evening, Los Angeles officials had counted more than 120 mudslides and 25 damaged structures in the city, many of which were in the hills above Hollywood and Beverly Hills.

Dozens of people had to attend throughout Southern California plucked from the floodwaters and the raging seas, including a man in Los Angeles County who jumped into the raging Los Angeles River to try to save his dog. In the Baldwin Hills neighborhood, a mud avalanche ripped through a bedroom of a house.

But overall, the region did not suffer the worst flooding and other impacts it had prepared for, said Los Angeles County Supervisor Lindsey Horvath.

“Instead, the damage amounted to more than a thousand cuts: sinkholes, fallen trees, areas of erosion,” she said at a news conference Monday evening.

Firefighters evacuated 16 people in the Studio City neighborhood on Monday after two homes on Lockridge Road suffered significant damage from debris sent by the storm sweeping through the area.

Residents walked the streets Monday morning, almost in a daze, looking at the piles of mud and jumble of stones scattered across the road. Ankle-deep water poured down a hill, carrying bits of debris. Some residents on the tree-lined streets near Lockridge Road cleared mud that had collected in their driveways as city maintenance trucks drove back and forth in an attempt to clear the road.

In other parts of Los Angeles, residents cautiously ventured back out into the world on Monday, splashing through intersections where water had collected. Although officials urged people to stay off the roads, nearly all campuses in the Los Angeles Unified School District remained open and classes were expected to resume Tuesday.

In Northern California, residents were still recovering from damage caused by heavy winds that reached more than 90 miles per hour in some locations Sunday. At one point, more than 850,000 businesses and homes were without power as winds knocked down power lines and damaged other electrical equipment. Pacific Gas & Electric, the state's largest utility, said Sunday it was among the top three outages ever due to storms.

The wind also turned deadly. A 41-year-old man in the Sacramento suburb of Carmichael and an 82-year-old man in Yuba City, north of Sacramento, were killed by falling trees in their backyards. A 45-year-old man died Sunday in the Santa Cruz Mountains when a tree fell on his house. The three deaths so far are the only fatalities from the storm.

The atmospheric river was expected to move south into the San Diego region on Tuesday, but isolated showers and thunderstorms were still likely in Los Angeles, said Ariel Cohen, a meteorologist with the National Weather Service in Los Angeles.

Mr. Cohen said the ground was extremely saturated after what he called one of the wettest storm systems to hit the Los Angeles area since record keeping began. He warned Angelenos Tuesday to remain vigilant, even as the sky appeared bluer.

“It won't take much rain before there are more landslides, rockslides and mudslides,” he said.

During a Monday evening news briefing, Los Angeles Mayor Karen Bass stepped away to take a call from President Biden. When she returned to the stage, she held her cell phone next to the microphone while the president was still on the other end of the line. Mr. Biden called the city's efforts over the loudspeaker “a great operation” and said he had just gotten off the phone with Gov. Gavin Newsom.

“We will get all the help as soon as you ask for it,” Mr. Biden said. 'So just let me know. That's why I'm calling.”

Jill Cowan contributed reporting from Los Angeles.