The Chicago skyline is seen beyond the arctic sea smoke rising off Lake Michigan in Chicago, Illinois.
The polar vortex, a deadly blast of Arctic air that shattered decades-old records as it gripped the middle United States moved eastward on Tuesday, canceling thousands of flights, paralyzing road travel, and closing schools and businesses.
Shelters for the homeless were overflowing due to the severe cold brought by a polar air mass that produced the coldest temperatures in two decades and at least four deaths.
The deep freeze snarled commuters with icy or closed roads and flight delays on Tuesday, with some 1,800 U.S. flights canceled and roughly 400 delayed, according to FlightAware.com, which tracks airline activity.
Gusty winds and bone-chilling temperatures hovering near 0 degrees Fahrenheit (minus 18 degrees Celsius) were to hit the mid-Atlantic region, including Pennsylvania, New Jersey, and New York, where Governor Andrew Cuomo had declared a state of emergency.
"It will be a frigid morning commute because temperatures are going to be below zero across parts of Pennsylvania, Ohio, even down into West Virginia," said Roger Edwards, a meteorologist with the National Weather Service.
Temperatures were 20 to 40 degrees Fahrenheit below average across the Great Lakes region. In the Duluth-area of Minnesota, temperatures plummeted to minus 24F to minus 26F (-31C to -32C).
Minneapolis public schools were to be closed for a second day on Tuesday "due to extremely cold temperatures," after Gov. Mark Dayton declared a state of emergency on Monday.
It was about minus 7F (-22C) in Chicago.
The frigid air was pushing eastward on Tuesday and would likely dump one to two feet of snow east of Lake Erie and Lake Ontario, Edwards said.
Many weather-related deaths were reported, including a 48-year-old Chicago man who had a heart attack while shoveling snow on Sunday and an elderly woman who was found outside her Indianapolis home early Monday.
While Tuesday's readings were likely the coldest of the week, Edwards said, "the frigid, freezing temperatures are going to linger."