The first major storm of the season was pounding the Western United States and was headed eastward Tuesday toward the Rockies in Colorado and New Mexico, the National Weather Service said.

Up to 3 feet of snow were expected in the Rockies, with winds up to 90 mph. The Sierras straddling California and Nevada already were knee-deep with 2 to 3 feet of snow, and a foot was forecast to fall in Iowa and Minneapolis, Minnesota.

Parts of both states are under a blizzard warning, forecasters said.

In Sacramento, California, it was 20 degrees -- unusually cold for this time of year, forecasters said. The city opened a shelter Monday and planned to leave it open until Wednesday evening.

In the southern part of the state, the California Highway Patrol shut down the Grapevine section of Interstate 5, a major north-south artery, near Gorman between Los Angeles and Bakersfield.

"They told us it was coming, and it's the Grapevine. It snows half an inch, and they shut it down," a motorist told CNN affiliate KTLA-TV.

Truck driver Ruth Sanderson enumerated the dangers of driving in snow in the mountains: "Being turned over, getting stuck up here and not going nowhere," she told CNN affiliate KABC-TV. "You go to the nearest exit and you park ... the best you can. You're stuck there until they open up the roads."

Fellow driver Karen Lobina took a softer view: "I like it. We need the snow, and it's good, even though it's a big hassle to drive in," she told KABC.

Fred Cable of Lebec said he hoped for a foot of snow, and he planned to snuggle up near his fireplace.

"My wife is good enough to bring up a bunch of firewood the last two days from work," he told KABC. "We love the snow. That's why we moved up here."

The storm was headed into the Plains states later Tuesday and into the Midwest by nighttime, then on to the Northeast. The storm will pick up moisture from the Great Lakes -- called the Great Lakes effect.

Apparently, the customers at Minneapolis' Bad Waitress Coffee Shop and Diner -- who are familiar with the white stuff -- weren't too worried the approaching storm.

"I haven't heard too much," said employee Ann Corn of the predicted snowfall. "I kind of expected it. I guess we're glad it came pretty late in the season."

Snow and sleet were raining down on Chicago, Illinois, by late Tuesday morning, delaying flights arriving at O'Hare International Airport by nearly two hours, according to the Federal Aviation Administration air traffic control center. That delay was affecting flights throughout the country.

The weather service predicted a low of 34 in Chicago on Tuesday night. The snow was to continue into Wednesday.

In Kansas City, Missouri, snow, freezing rain and sleet were expected to snarl afternoon rush-hour traffic. The overnight low will dip to 15 degrees, forecasters said.

Blowing and drifting snow in the Northern Plains and Upper Midwest were expected to reduce visibility, likely leading to closures of major highways.

It was raining in the South, including in Atlanta, Georgia, where wet weather was forecast to continue through Tuesday night.