CHICAGO (Reuters) - Bone-chilling cold swept across the snow-hit Great Plains and Midwest on Monday, closing schools and playing havoc with travel plans, with the sub-freezing temperatures reaching as far south as Florida.
Minnesota and Wisconsin shivered in temperatures not expected to top single digits -- with wind-chills much colder than that -- and motorists spent hours awaiting rescue on impassable roads in northwest Indiana.
Air traffic was gradually returning to a semblance of normal after hundreds of flights were canceled at airports in Midwestern and East Coast hubs during the worst of a snow storm on Sunday.
Another 75 flights were canceled at O'Hare International Airport on Monday, but delays were called minor.
"We aren't anticipating any more cancellations," said American Airlines spokeswoman Mary Frances Fagan.
There were winter storm warnings posted for parts of West Virginia, Kentucky, Tennessee, western Pennsylvania, western New York and Vermont, forecasters said.
Pittsburgh braced for up to four inches of snow on Monday and another six inches by early Tuesday, according to the National Weather Service.
"Cities that will have enough snow to cause travel trouble this time around will include Indianapolis, Cleveland, and Pittsburgh," said AccuWeather.com meteorologist Justin Povick.
Lake-effect snows -- generated when cold air whips up storm clouds off the warmer Great Lakes -- continued to plague northwest Indiana, northern Ohio, and western New York.
While Midwestern skies had mostly cleared, the landscape was ice-bound and blanketed with snow.
Ice-clogged locks and dams along the Mississippi and Illinois Rivers slowed commercial barge traffic. Barge tows required 20 hours instead of the usual 90 minutes to pass through the Mississippi River lock near Canton, Missouri.
In Minneapolis, where the Metrodome stadium's inflatable roof collapsed on Sunday under the weight of 17 inches of snow, schools were closed. Concerns were raised about children waiting in the cold if buses got delayed on snowbound roads.
Schools in Nashville, Tennessee, were also closed as a coating of snow made for treacherous road conditions.
There were a few storm-related deaths over the weekend attributed to the snow storm, including a 79-year-old St. Croix County, Wisconsin, man killed when a snow plow ran into him while he was clearing his driveway.
The frigid weather was supposed to last through mid-week, with another storm arriving in the Midwest on Thursday, the National Weather Service said.
The stunning exception was the Southwest. Phoenix residents basked in record-breaking 80-degree warmth.
But in the southeast, temperatures dipped below 20 degrees with light snow that forced the closing of some schools and roads, authorities said.
"We've had an increase in accidents on the roads," said Yasamie Richardson, spokeswoman for the Alabama Emergency Management Agency. "Some schools have been closed."
A torrential weekend rain storm triggered river flooding and mudslides in the U.S. Northwest, shutting down Amtrak passenger rail service between Seattle and Portland, Oregon.
Flood warnings were issued for parts of nine rivers across western Washington from Bellingham south to Olympia. An approaching storm was forecast to dump 10 inches of snow on the Cascades.
(Additional reporting by John Rondy in Milwaukee, Karl Plume in Chicago, Laura Myers in Seattle, Steve Gorman in Los Angeles, David Beasley in Atlanta, Ellen Wulfhorst in New York; Editing by Andrew Stern and Peter Bohan)