LOS ANGELES — Snow and ice in whiteout conditions contributed to a pileup of more than 100 cars on a major highway connecting Oregon and Idaho, reportedly injuring several people, as a winter storm descended on the Pacific Northwest Thursday.

To the south, Southern California braced for heavy rains accompanying the strongest atmospheric river of the season with evacuations ordered in some Los Angeles neighborhoods ravaged by wildfires at high risk of mudslides.

The West Coast storms are just the latest in a week of bad weather across the U.S. that cut power to tens of thousands.

Pacific Northwest Ice Storm

First responders were searching every vehicle that was involved in the massive pileup near Multnomah Falls, about 25 miles (40 kilometers) east of Portland, the Multnomah County Sheriff’s Office said on social media.

The pileup happened in whiteout conditions in the westbound lanes of Interstate 84, authorities said, noting that an SUV caught fire but its occupants escaped. The sheriff’s office said there were reports of injuries and people being trapped in their vehicles. Oregon State Police spokesperson Kyle Kennedy said in an email that there have been no reported deaths.

Freezing rain and snow contributed to the pileup in Multnomah County, where officials extended a state of emergency through at least Friday and said eight emergency shelters would be open. Officials said 489 people went to the shelters Wednesday night. Wind chill readings could dip to 10 degrees (minus 12 Celsius) in Portland, the weather service said.

Northwestern Oregon, including Portland, could see up to 3 inches (7.6 centimeters) of snow with winds gusting as high as 45 mph (72 kmh), according to the weather service. In southern Washington state, six people were taken to hospitals with injuries in multiple crashes involving more than a dozen vehicles on Interstate 5 near the Cowlitz River, said state patrol spokesperson Will Finn.

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Too Much Rain Too Quickly in California?

Southern California could get as much as 6 inches (about 15 centimeters) of rain in the mountains and 3 inches (nearly 8 centimeters) in coastal areas and valleys before the system moves out Friday, said Brent Bower, a National Weather Service hydrologist. Powerful gusts could bring down trees, cause power outages and delay flights.

Evacuation orders and warnings were issued in areas where hillsides were scarred by the Palisades Fire, the most destructive in LA history. Scorched areas are at risk of mudslides because vegetation that helps keep soil anchored has been burned away. The fires also added loose debris to the landscape, including ash, soil and rocks.

Officials distributed sandbags, prepositioned rescue swimmers and told residents to have go-bags ready. Sandbags and temporary concrete barriers were in place across Altadena, where the Eaton Fire destroyed thousands of homes.

“If you can, stay off the roads today, especially this afternoon and evening,” the weather service office for Los Angeles posted on X.

Malibu schools were closed Thursday. In Orange County to the south, the Knott’s Berry Farm amusement park closed due to the atmospheric river, a long band of water vapor that forms over the ocean and transports moisture from the tropics to northern latitudes.

Despite recent storms, much of Southern California remains in extreme or severe drought, according to the U.S. Drought Monitor. Daniel Swain, a climate scientist with the University of California, Los Angeles, said that while the area is desperate for rain, this storm might bring too much too quickly.

In the San Francisco Bay Area, there were power outages, small landslides and inundated roadways. North of the city in wine country, concerns were high along the flood-prone Russian River. Authorities urged people to evacuate Felton Grove, a small community along California’s central coast, as the San Lorenzo River threatened to spill over its banks.

In neighboring Nevada, the weather service said it recorded a measurable amount of rain in Las Vegas Thursday, ending a dry streak of 214 days without precipitation.

The East Is Hit With Heavy Snow and Freezing Rain

School was canceled or delayed on Thursday in dozens of districts in New England, where snow and ice made driving dangerous. Maine State Police said they were investigating a crash involving a tractor trailer on the Maine Turnpike that killed two people.

Thursday’s storms followed two days of heavy snow and freezing rain in a swath of the eastern U.S. stretching from Kentucky to Washington, D.C., that caused hundreds of traffic accidents, knocked out power to tens of thousands and threatened to flood waterways.

By Thursday afternoon, nearly 175,000 customers in Virginia and about 14,000 in North Carolina were still without electricity, according to PowerOutage.us.

Nearly 3,500 flights to or from U.S. airports were canceled or delayed Thursday, according to the flight-tracking site FlightAware.com.

Two Tornadoes in Mississippi

The National Weather Service confirmed two brief EF-0 tornadoes in Mississippi on Wednesday, including one that shredded the steel roof of an industrial building and damaged several homes in Columbia. No deaths or major injuries were reported, Columbia Mayor Justin McKenzie told WDAM-TV.