The so-called "polar vortex" of dense, frigid air that spread across the country shattering temperature records is being blamed for at least 21 deaths.
Authorities reported at least 21 cold-related deaths across the country since Sunday, including seven in Illinois and six in Indiana. At least five people died after collapsing while shoveling snow, while several victims were identified as homeless people who either refused shelter or didn't make it to a warm haven soon enough to save themselves from the bitter temperatures.
In Missouri on Monday, a 1-year-old boy was killed when the car he was riding in struck a snow plow, and a 20-year-old woman was killed in a separate crash after her car slid on ice and into the path of a tractor-trailer.
In a phenomenon that forecasters said is actually not all that unusual, all 50 states saw freezing temperatures at some point Tuesday. That included Hawaii, where it was 18 degrees atop Mauna Kea, a dormant volcano.
New York City's Central Park broke a 118-year-record Tuesday morning when the temperature there dropped to 4 degrees. Its previous record of 6 degrees had stood since 1896, according to MyFoxNY.com .
Charlotte, N.C., reached 6 degrees, breaking the 12-degree record that had stood since 1884.
Farther south, Birmingham, Ala., dipped to a low of 7, four degrees colder than the old mark, set in 1970. And temperatures also hit lows in parts of West Virginia not felt for 25 years, while the extreme cold in Virginia Tuesday beat record lows that had stood since the late 1950s.
The big chill started in the Midwest over the weekend, caused by a kink in the "polar vortex," the strong winds that circulate around the North Pole. The icy air covered about half the country by Tuesday, but it was moving north, returning more normal and warmer weather to most of the country. This weekend, it was expected to be in the 50s in New York and even higher in places farther south along the Eastern Seaboard.
On Tuesday, many schools and day care centers across the eastern half of the U.S. were closed and officials opened shelters for the homeless and anyone else who needed a warm place.
"I didn't think the South got this cold," said Marty Williams, a homeless man, originally from Chicago, who took shelter at a church in Atlanta. "That was the main reason for me to come down from up North, from the cold, to get away from all that stuff."
In the Midwest and East Wednesday morning, where brutal polar air has lingered over the past few days, temperatures climbed but were still expected to be below freezing. An estimated 190 million people in the U.S. were subjected to the polar vortex's icy blast.
Chicago Public Schools officials said the nation's third-largest school district will resume classes Wednesday after closing for two days because of the cold and idling 400,000 students.
In Indianapolis, Timolyn Johnson-Fitzgerald returned to her home after spending the night in a shelter with her three children because they lost power to their apartment. The water lines were working, but much of the food she bought in preparation for the storm was ruined from a combination of thawing and then freezing during the outage.
"All my eggs were cracked, the cheese and milk was frozen. And the ice cream had melted and then refroze. It's crazy, but we're just glad to be back home," she said.
The bitter cold had slowed baggage handling and aircraft refueling at airports, forcing airlines to cancel thousands of flights.
As of Wednesday morning, more than 900 flights were canceled across the U.S. and more than 2,500 were delayed, according to the flight tracking website FlightAware.com.
On Tuesday, more than 3,286 flights were canceled and more than 9,660 were delayed, FlightAware.com statistics show.
Some passengers – like those stuck at Boston’s Logan Airport – remained grounded for days until service resumed.
Across the South, the Tennessee Valley Authority said power demand reached the second-highest winter peak in the history of the Depression-era utility. Temperatures averaged 4 degrees across the utility's seven-state region.
In South Carolina, a large utility used 15-minute rolling blackouts to handle demand, but there were no reports of widespread outages in the South.
Natural gas demand in the U.S. set a record Tuesday, eclipsing the mark set a day earlier, according to Jack Weixel, director of energy analysis at Bentek Energy.
The Associated Press contributed to this report.