LOS ANGELES — As rare blizzard conditions continued to present hazards in the mountains of Southern California on Saturday, residents at lower elevations dealt with the fallout from a more familiar threat: flooding.

Intense rains and powerful winds that pounded Los Angeles and surrounding counties on Friday night and early Saturday produced significant flooding in urban areas, downed trees and threatened to cause debris flow and mudslides.

Multiple water rescues have been conducted across counties because of rising waters, said Ariel Cohen, a meteorologist for the National Weather Service in Los Angeles. One person in Santa Barbara County, which also experienced some flooding, was injured after strong winds caused a tree to fall into a home, and in Inglewood, falling trees crushed a line of cars, taking out power lines, he said.

One person died after a vehicle drove off the road and into a flood control area, though it was not immediately clear whether the death was related to the storm, said Kerjon Lee of Los Angeles County Public Works.

Meteorologists said that the most severe effects of the storm at lower elevations could be over, though flood watches remained in effect in parts of Los Angeles and Ventura County, according to the National Weather Service.

A flood warning was also in place for the Santa Ynez River in Santa Barbara County until Saturday evening, threatening nearby farmland and the city of Lompoc.

Early Saturday morning, the Los Angeles River near Long Beach was rapidly flowing toward the ocean. Water levels in the river bed were high, although no flooding was visible.

Portions of Interstate 5 winding through Los Angeles County — including the Grapevine, a 40-mile stretch that goes up to Kern County — were closed on Saturday morning because of flooding, snow and mudslides. And a 20-mile stretch of State Route 14 in Acton, an unincorporated area in northern Los Angeles County, was closed Saturday morning, snarling south-bound traffic for miles.

It is rare for the stretch of freeway, lying around 2,000 feet above sea level, to close because of weather conditions, said Eric Menjivar, a spokesman for Caltrans, California’s Department of Transportation, referring to State Route 14. Working 12-hour shifts, 24 hours a day, work crews had plowed more than 200 miles of freeway lanes by Saturday morning. The elevations where snow fell “really dropped last night,” he said.

“We’re having a lot of flooding,” Mr. Menjivar said. “It’s a slow-moving storm and the rain has been really consistent.”

More than 17,000 electricity customers in the Los Angeles region were also without power on Saturday, according to Southern California Edison. Statewide, more than 117,000 customers were without power, according to the tracker poweroutage.us.

On Saturday afternoon in Los Angeles, the rain, which had stopped in the late morning, grew heavy again. The weather left some residents scrambling to change their weekend plans for outdoor events, typically a sure thing this time of year in Los Angeles. The season-opening match on Saturday between Major League Soccer crosstown rivals L.A. Galaxy and LAFC in Pasadena was postponed because of forecasts that included potential lightning.

Six Flags Magic Mountain in Los Angeles County and Knott’s Berry Farm in Orange County were closed, and Little League opening day parades were canceled because of wind and rain.

“It’s been a big disappointment,” said Tracey Lee, 48, a resident of the coastal community of Palos Verdes Estates near Los Angeles, who had spent three months planning opening day celebrations for the local Little League.

The festivities included a two-mile parade of double-decker buses, trolley cars and floats on trailers led by police and fire vehicles down one of the small city’s main thoroughfares. About 2,000 people were expected to be at the event as participants or spectators.

“We don’t have another choice,” she said, lamenting the cancellation. “They say you live in this area for two reasons: Halloween and opening day. It’s something the whole community looks forward to every year.”

Along with the disappointment, Ms. Lee said her neighborhood also experienced power outages during the week and downed trees.

The storm has already set records. On Friday, Los Angeles International Airport received a record 2.04 inches of rain. Earlier in the week, Los Angeles County issued its first blizzard warning since Feb. 4, 1989.

“It’s been many years since we’ve had such a widespread coincidence of all of these hazards at the same time,” Mr. Cohen said.

The United States and other countries have already seen more frequent extreme rainstorms as the world warms. The frequency is likely to increase as warming continues, in part because warmer air holds more moisture.

Almost 15 inches of rain have fallen in parts of Los Angeles County over the past four days, the Weather Service estimated.

In the mountains around Los Angeles, blizzard warnings remained in effect. More than four feet of snow has already accumulated, and the total could double, with whiteout conditions on roads.

In Northern California, which felt the impact of this storm earlier in the week, residents are facing another dose of wintry weather early next week. Yosemite National Park announced that it would be closed through Wednesday because of rain, wind and snow that were forecast.

Despite all the disruptions and inconveniences, some residents were not fazed by the weather.

“I love when all this stuff happens. I love all the rain we have been getting this year,” said John Carter, who was with his wife, Christina, at a Panera Bread in Corona, a town about 50 miles southeast of Los Angeles.

Mr. Carter, 46, a 911 dispatch operator for the Anaheim Police Department, said he loves the change and that he and his wife were looking forward to the spring poppies bloom, which was already happening in the hills along the highway near their home in unincorporated Riverside County.

Ms. Carter, 47, who works in administration with Southern California Edison, said the rain made all the foothills around them green, “and you get to see something different than your everyday dusty brown.”

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