Parts of California were pounded with another wave of rain on Monday in the latest storm to test the state after a deadly deluge caused widespread power outages and destructive mudslides two weeks ago.
In the Bay Area, thunderstorms, wind gusts and lightning moved into the region on Monday afternoon, with forecasters warning of a possible “land spout” — a weak tornado likely caused by a water spout reaching land — in southwestern San Mateo County, south of San Francisco.
Around the same time, a line of thunderstorms was sweeping over the northern Central Valley. Daniel Swain, a climate scientist at the University of California, Los Angeles, said those storms could cause flooding or flash flooding. Forecasters warned of quarter-size hail and a potential tornado.
Dr. Swain said he also worried about similar possible storms in the Sacramento area.
More rain was expected over the next few days, with flood watches in effect for millions of people, mostly in California, through Wednesday.
The rain is coming from an atmospheric river, a type of storm in which Pacific winds blow narrow, intense bands of moisture over the West Coast. They often cause California’s heaviest rain, snow and floods.
“It’s just a huge swath of moisture,” said Rich Thompson, a meteorologist with the National Weather Service in Los Angeles.
Southern California bore the brunt of the storm early Monday. Between two and 10 inches of rain had fallen in Ventura and Santa Barbara counties, with the highest totals in the foothills of the mountains, according to the Weather Service. The airport in Santa Barbara shut down on Monday because of flooding on the airfield.
Mr. Thompson said there had been many reports in the morning of “roadway flooding, some rocks and debris across road ways, road closures.”
“The soil is so saturated from the previous storm that this rain has nowhere to go,” he said, adding, “We’re a long way from this being over.”
While only light rain had made its way south to Riverside, Orange and San Bernardino counties by midmorning on Monday, steady rain pelted Los Angeles, and the California Highway Patrol was busy clearing vehicle crashes. Northwest of Los Angeles, at the beach in Ventura, a few hardy kite surfers were braving the elements.
Flash flood warnings were in effect through Monday evening for the Santa Monica Mountains, Hollywood Hills and Beverly Hills.
Farther north, the San Francisco Peninsula, which includes the city of San Francisco, was expected to receive up to 2 ½ inches of rain. Rainfall of three to five inches was expected in the Santa Cruz Mountains, and three to six inches along the Big Sur Coast.
Much of the Sacramento Valley was put under a wind advisory through Tuesday morning. One man who was camping near a creek in El Dorado Hills, east of Sacramento, was rescued from surging floodwaters early Monday, KCRA-TV reported.
Officials in Santa Barbara and Los Angeles counties issued evacuation warnings for certain vulnerable communities. On Monday morning, the authorities in Santa Barbara found a woman’s body in Mission Creek. A Santa Barbara Police Department spokesman, Sgt. Ethan Ragsdale, said it was too early to tell whether her death was related to the storm, but the police said no foul play was suspected.
Mission Creek can turn into a raging river during heavy rainfall; during the storm two weeks ago, the creek overflowed its banks, prompting some home evacuations.
Under a light drizzle on Monday afternoon in Santa Barbara, Mark Maslan and his wife, Ann Cumming, walked by the swollen creek. They have lived in town since 1990 and near the creek for about two decades.
“We’re glad that the reservoirs are filling and it’s good for drought conditions, but I wonder about the resiliency of the infrastructure,” said Mr. Maslan, an English professor at the University of California, Santa Barbara. “This creek overflowed once and it seems like it’s becoming a regular threat.”
In Los Angeles, Mayor Karen Bass had implored residents over the weekend to prepare.
In the city’s hilly neighborhoods, homeowners and workers spent Sunday preparing sandbags and laying plastic tarps over muddy hillsides that still bore the scars of the last storm.
Some residents, including Staci Broussard, 58, took care to reinforce their properties soon after that storm ended. Ms. Broussard’s home in Baldwin Hills Estates, a neighborhood overlooking South Los Angeles, was damaged by the previous atmospheric river to rip through the city.
The slope behind Ms. Broussard’s home crumbled, knocking down a portion of her backyard iron fence, bringing mud and vegetation down the hill from her neighbor’s home on a hill above.
Ms. Broussard and her neighbor staked down tarps over the hillside to prevent more mud from sliding down.
“As you can see, we have tarps all over because this is happening all over this neighborhood, unfortunately,” she said on Sunday.
Vik Jolly reported from California, and Sarah Mervosh and Orlando Mayorquin from New York. Patricia Mazzei contributed reporting.
