The system closed roads and delayed flights from Anchorage to Salt Lake City on some of the busiest travel days of the year.
Meteorologists warned residents in the Dakotas to expect a range of messy wintery weather, from freezing drizzle in the eastern two-thirds of South Dakota to a possible blizzard in eastern North Dakota.
"Like the Boy Scouts, you've got to be prepared for a North Dakota winter or you're asking for your own problems," said Gerald Miller, 52, who plowed roads on his farm just east of Bismarck on Wednesday.
Miller has spent every winter of his life in North Dakota except for one in 2003 when he served in Iraq with the National Guard. "After Iraq, I promised I'd never complain about the weather in North Dakota again," he said.
Blowing snow was likely to cause problems for holiday travelers even in areas not expected to get significant amounts.
"We have snow on the ground in many areas, and any snow on top of that will combine for the potential to blow around, reduce visibility and drift, and cause problems for people trying to drive," meteorologist Jeff Savadel said.
State officials in both Dakotas issued statements urging people to be cautious.
In South Dakota, truckers carefully navigated the icy roads, with snow expected later in the day.
"It's getting bad," said Bob Grape, who had stopped at a gas station in Sioux Falls on his way north. Grape said he would keep moving through the weather unless it got significantly worse.
"There isn't a load of freight that's important enough to risk your life," he said.
In Iowa, at least three people died in weather-related crashes as freezing rain and drizzle left roads with a light glaze.
There were 23 accidents during the day Wednesday, police said. State officials say many northern Iowa roads were covered with ice and many schools in the region were closed early.
The storm system buried Seattle in snow, causing at least three deaths, and shut down highways for a time in Idaho, Wyoming and Utah. It also brought high winds on Wednesday to New Mexico and northern Arizona.
The roads were less chaotic in Utah on Wednesday. On Tuesday night, there were 118 traffic collisions and 119 vehicles that slid off the road, police said.
National Weather Service snow totals showed that it wasn't the quantity of snow that made for treacherous driving.
Most cities in Utah received less than 6 inches in the previous 24 hours -- an amount residents here are accustomed to. Instead, the danger largely came from high winds blowing snow at night that made it difficult.
"A lot of people heeded the message, stayed off the road and cut down on a lot of problems," Utah Highway Patrol Trooper Todd Johnson said. "The crash figures -- they're not as high as I expected them to be."
(Copyright 2010 by The Associated Press. All Rights Reserved.)