At least five people were killed and several others were injured on Tuesday by falling trees in California, where heavy rain and snow have repeatedly walloped weather-fatigued residents, officials said.

Strong winds and precipitation associated with this week’s rush of dangerous storms were expected to subside on Wednesday before moving into the Southwest, the National Weather Service said.

One man died Tuesday afternoon after a tree fell on his vehicle in San Mateo County, just south of San Francisco, said Officer David LaRock, a spokesman for the California Highway Patrol.

“That tree went down due to high winds and over saturation of water we’ve received in the last few weeks,” he said.

Fire officials in Contra Costa County, just northeast of San Francisco, said on Tuesday that another large tree had fallen onto a car, killing the passenger and injuring the driver. Two more people were killed and three others were injured by falling trees in the San Francisco area, officials said.

In Oakland, a homeless man was killed when a 50-foot tree fell on the tent he was inside at Lake Merritt, The Associated Press reported.

As snow covered portions of Interstate 80 in Northern California on Tuesday, flooding prompted the temporary closure of other roadways further south, including several in Santa Cruz County and a portion of the Pacific Coast Highway, south of Los Angeles. Officials said that an Amtrak train had also crashed into a tree near Martinez, Calif., but that there were no injuries.

By Wednesday afternoon, close to 90,000 utility customers statewide were without power, mainly in the San Francisco Bay Area, and millions of residents were under flood watches. A rare tornado warning had briefly been issued west of Los Angeles.

In Montebello, southeast of Los Angeles, videos were circulating on social media on Wednesday of what appeared to be a tornado tearing off portions of roofs and tossing debris into the sky. It was unclear if there were any injuries.

Windows in four high-rise buildings across San Francisco were also broken by high winds, said Patrick Hannan, a spokesman for the city’s building inspection department. Each tower, he added, had 14 days to repair the windows. There were also reports of over 700 fallen trees and limbs across the city, according to the mayor’s office.

The National Weather Service office in Oxnard, Calif., said in an update on Wednesday that it would send a team to survey the damage in the Montebello area, as well as in southeast Santa Barbara County, where there were reports of a possible tornado that damaged mobile homes on Tuesday.

The “atmospheric river” storm system brought several inches of rain to parts of Southern California by Wednesday morning, raising the potential for more flooding in areas where soil was already saturated from weeks of precipitation, according to a Weather Service forecast.

Higher elevations recorded a couple of feet of snow, with more possible on Wednesday, creating the possibility of avalanches, the agency said.

Warnings about winter weather and high winds were gradually lifted across the state on Tuesday evening. The storm was not expected to bring as much moisture to the state as some of the recent atmospheric rivers that had inundated Central California.

But it was still causing trouble in several counties.

In the Bay Area, Stanford University canceled final exams on Tuesday because of a widespread power outage, the school’s emergency information center said. One of the main transmission lines that feeds the campus was affected by the storm. Exams were expected to resume on Wednesday.

In the Sacramento area, forecasters warned of hail, lightning and gusty winds in some areas as rain fell in a north-south band from Redding to San Francisco on Tuesday night.

In Central California, the authorities were keeping an eye on extremely high water levels in rivers, creeks and steams. They said heavy rain below 4,000 feet could cause flooding into Wednesday night.

Meteorologists were also tracking heavy thunderstorms moving across Tulare County, which has been flooded during previous storms this year. Officials had started going door to door there on Sunday to urge residents in portions of that county to evacuate.

The Tulare County Sheriff’s Office said Tuesday night that there were reports of damages to roadways in the area, including sinkholes, mudslides, washouts and flooding.

On Tuesday evening in Southern California, the Weather Service issued a rare tornado warning for parts of Ventura and Los Angeles Counties. The warning expired after 12 minutes, and the Ventura County Sheriff’s Office later said that there was no evidence a tornado had touched down in the area.

The system was expected to have less moisture than the recent back-to-back storm systems that brought heavy rain and flooding to Central California, said Ashton Robinson Cook, a meteorologist with the Weather Service’s Storm Prediction Center.

“We don’t think the rain totals will be as extreme,” Mr. Cook said on Monday. “We’re not expecting the impacts to be nearly anything like what we experienced, especially in Central California, last week.”

The United States and other parts of the world have already seen an increase in the frequency of extreme rainstorms as the world warms. The frequency is likely to increase as warming continues. One basic reason is that warmer air holds more moisture.

California is trying to recover from a series of storms that have brought heavy rain and snow, causing flooding in portions of the state. It is the second snowiest season in the Central Sierras since researchers at the University of California, Berkeley, began keeping records in 1946. This season, 677 inches of snow have fallen there, the researchers said, compared to a record 812 inches in 1952.

In January, an atmospheric river prompted evacuation orders for more than 40,000 Californians and left more than 220,000 utility customers without power. That storm was part of a three-week series of atmospheric rivers that inundated much of the state, damaging infrastructure and setting off flooding.

The severe weather events in California continued into February, when storms brought heavy flooding to Los Angeles County and whiteouts at higher elevations, and into March, when Gov. Gavin Newsom declared a state of emergency in several counties affected by winter storms that dumped as much as 10 feet of snow in parts of Southern California, leaving some people stranded for days.

After that storm, yet another atmospheric river hit California. It washed out portions of roadways, prompted evacuations, caused power outages — particularly in the central region — and contributed to at least one death.

Livia Albeck-Ripka, April Rubin and Derrick Bryson Taylor contributed reporting.