Homes are seen covered in snow and ice on Wednesday in Chicago.
An arctic blast eased its grip on much of the eastern U.S. on Wednesday, with winds calming and the weather warming slightly a day after temperature records - some more than a century old - shattered.
Authorities reported at least 21 cold-related deaths across the country since Sunday. 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.
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 (-8 Celsius) atop Mauna Kea, a dormant volcano.
In Atlanta, where a record low of 6 degrees Fahrenheit (-14 Celsius) hit early Tuesday, the forecast Wednesday was sunny and a more normal 42 degrees (5 Celsius).
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.
With the bitter cold slowing baggage handling and aircraft refueling, airlines canceled more than 2,000 flights Tuesday in the U.S., bringing the four-day total to more than 11,000.
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.