An ice storm struck Iowa and eastern Nebraska over the weekend, shutting down a major interstate highway as cars and trucks slid off of the road. At least one person was killed in a crash because of the icy roads in Nebraska.

The National Weather Service in Des Moines issued a dense fog advisory Saturday that was set to remain effective through 11 a.m. CT Sunday. Thick fog spread across much of the state, reducing visibility to 1/4 of a mile or less in some places, the weather service said. Ice had predominantly turned into freezing rain by Saturday evening, but roads in eastern Iowa were still at least partially blanketed by ice or snow, the forecasters said.

Authorities said one person died while driving on icy roads in eastern Nebraska. The Washington County Sheriff’s Office said a 57-year-old woman was killed in a crash after losing control of her pickup truck on Highway 30, near Arlington, and hit an oncoming truck. The other driver sustained minor injuries in the accident. Washington County is located close to the eastern Nebraska border with Iowa, near Omaha.

Roads in that area were slick enough Saturday to play ice hockey in the street, as one person was seen doing in a social media video that the National Weather Service in Omaha reposted. A dense fog advisory was also in pace for the region through Sunday at 11 a.m. CT.

“Dense fog is continuing to develop across our area and is expected to last through tomorrow morning,” the National Weather Service in Omaha wrote in an advisory Saturday night. “With visibilities below a quarter mile at times and slick spots redeveloping on some roadways, please exercise caution and take things slow if you’re out and about!”

Forecasters warned untreated roads could refreeze overnight as temperatures dropped.

Many events were canceled across the region when the storm hit Friday evening, and businesses announced plans to open late Saturday as officials urged people to stay home if possible. Temperatures rose high enough in the afternoon to melt the ice in most places, however.

“Luckily some warmer air is moving in behind this to make it temporary,” said Dave Cousins, a meteorologist with the National Weather Service’s office in Davenport, Iowa.

Elsewhere, a storm and wind gusts of up to 60 mph prompted the first tornado warning in San Francisco and caused some damage. Parts of neighboring San Mateo County were also included in the warning, which went out at 5:51 a.m. to about 1 million people and was lifted about 20 minutes later.

Later Saturday, a tornado touched down near a shopping mall in Scotts Valley, near the city of Santa Cruz about 70 miles south of San Francisco, overturning cars and toppling trees and utility poles, the National Weather Service said. 

“Based on video, photos, firsthand accounts, and radar signatures a tornado occurred (at) 1:40 PM” PT, the service said, adding that a team will investigate and provide a ranking.

Images uploaded to social media showed at least three vehicles on their hood or side, with their windshields smashed and trees and power lines on the ground.

Several people were injured and taken to hospitals, the Scotts Valley Police Department said.

“The tornado has caused extensive damage in several areas, including overturning several vehicles in and around the shopping district on Mt. Hermon Drive,” the department said in a statement. It asked people to avoid the area.

One of those injured was a battalion chief with the California Department of Forestry and Fire Protection, KSBW-TV reported.

In San Francisco, some trees toppled onto cars and streets and damaged roofs. The city has not seen a tornado since 2005, according to the Weather Service. The damage was being assessed to determine if the city was indeed hit by a tornado.

“This was the first ever warning for a possible tornado in San Francisco. I would guess there wasn’t a clear signature on radar for a warning in 2005,” said Roger Gass, a meteorologist in the Weather Service’s Monterey, California. He said he was not there in 2005.

The fast-moving storm prompted warnings for residents to take shelter, but few people have basements in the area.

“The biggest thing that we tell people in the city is to put as many walls between you and the outside as possible,” Meteorologist Dalton Behringer said.

In upstate New York, people were digging out after heavy snow fell. More than 33 inches was reported near Orchard Park, where residents are used to dealing with lake-effect snow this time of year.

And in Nevada, up to 3 feet of snow was forecast for Sierra Nevada mountaintops. More than a foot (30 cm) fell at some Lake Tahoe ski resorts, and a 112-mph gust of wind was recorded at the Mammoth Mountain resort south of Yosemite National Park, according to the National Weather Service’s Reno office.

A winter storm warning was set to expire at Saturday at 10 p.m. PT, but an avalanche warning remained in effect into the following night for elevations above 8,000 feet around Tahoe.

Interstate 80 was closed along an 80-mile stretch from Applegate, California, to the Nevada line just west of Reno, where rain was falling and a winter weather advisory was in effect through the afternoon. The California Highway Patrol reopened the road in the afternoon for passenger vehicles with chains or four-wheel drive and snow tires, though it remained closed to semitrailer trucks.

In western Washington, tens of thousands of people lost electricity Saturday, local news outlets reported, amid a system that brought rain and gusty winds.