ATLANTA -- Snow and blustery winds blew into the already-frigid East on Friday and a deep freeze settled into the Deep South, making highways especially hazardous in a region unaccustomed to the chilly temperatures.
Arctic air continued to blanket much of the nation a day after a tractor-trailer jackknifed on a snow-slick Ohio road and hit a van carrying disabled adults, killing four people.
In Atlanta, more accustomed to winter temperatures in the low 50s, a glaze of ice coated roads Friday after light snow overnight melted and froze. Nearly 30 cars piled up in a pre-dawn crash near Hartsfield-Jackson Atlanta International Airport.
"I wanted to stay home today, but my boss never called me back, so I thought I should try to get in," said Beth Ament, 30, who was fueling her car so she could get to a nearby transit station to take the train to her job in downtown Atlanta.
In Alabama, packed shelters brought out extra cots and opened doors for people fearful of the deadly cold.
"You have to be inside the way it is now. If you're not, they'll find you stiff," said Elizabeth Austin, a homeless woman who sought warmth at an inner-city Birmingham church.
Multiple deaths have been blamed on this week's cold, including a 44-year-old man whose body was found face-down in the snow early Friday in Billings, Mont. Schools in at least 10 states were closed, as were many roads and government offices.
The edge of the storm reached the Philadelphia area overnight. The National Weather Service said 5 to 7 inches of snow was expected across western Pennsylvania. In Pittsburgh and the surrounding areas, it has snowed every day since New Year's, a stretch that meteorologists say is unusual.
Travel was beginning to return to normal Friday at Chicago's airports, after a storm that dumped about 8 inches of snow.
The Chicago Department of Aviation said there were still minor delays at O'Hare International Airport because crews had to deice aircraft before they could take off.
Some Nebraska cities were cut off because highways leading in and out of town were blocked or all but impassable.
Amtrak announced that its train between Chicago and Denver wouldn't operate on Friday because of blowing and drifting snow in Nebraska.
In Ohio, a winter storm warning was in effect until Saturday morning. That's on top of the snow that had already coated Interstate 70, where a tractor-trailer spun out of control Thursday, crossed the median and swerved into oncoming traffic, colliding with a small bus transporting adult disabled passengers, the Ohio Highway Patrol said.
Three passengers on the bus were killed, as was its driver. Six other passengers on the bus, which was carrying 11 people, were injured, as was the driver of the commercial truck, Sgt. Raymond Durant said.
Snowfall was heaviest in Minnesota and parts of South Dakota, where some drifts were too big for snowplow drivers to clear.
Nowhere was it colder than in Bismarck, N.D., where wind chills hit 52 below zero Thursday and the temperature reached 14 below. Wind chills were still near 50 below in the Dakotas for a second day.
While North Dakotans get plenty of practice with bundling up, folks in other parts of the country were still learning the basics.
With temperatures on the Texas-Mexico border descending near freezing Thursday night, officials in Laredo issued an advisory telling residents to "dress warmly and stay dry."
In Mobile, Ala., hit by a rare arctic chill on the coast, Salvation Army spokesman Stacey Killingsworth said shelters were "filled to the brim." One that normally holds up to 28 homeless men a night has been averaging 115 in recent days, she said.
"We don't turn anyone away, including women and children. We've used cots and mats. We've put people in the auditorium and hallways," she said.
In Florida's Panhandle, vapor was rising off the Gulf as warm water met the frigid air.
"It's so cold that sparrows that have crawled under the plastic on our heated deck don't want to leave," said Scooter Montgomery, manager of Peg Leg Pete's Oyster Bar on Pensacola Beach.
AP Writers Melissa Nelson in Pensacola, Fla., and Jay Reeves in Birmingham, Ala., contributed to this story.