After days of an arctic chill so cold that a Chicago zoo brought their polar bear inside, the United States woke up to a break in the weather.
The National Weather Service said that "a much anticipated warm up" was expected over the eastern two-thirds of the US, which had shivered through a week of record-breaking cold and two massive snowstorms.
But it was still long-underwear and scarf weather for many on Wednesday, with the weather service predicting temperatures 8 to 14 degrees Celsius below average in parts of the Midwest.
Even normally warmer US states were affected, with only Hawaii escaping the below-freezing temperatures.
"I didn't think the south got this cold," said Marty Williams, a homeless man in Atlanta, Georgia. "That was the main reason for me to come down from up north, from the cold, to get away from all that stuff."
Air travel, which had been a nightmare for travellers with more than 18,000 flights cancelled since Thursday, was starting to slowly return to normal.
On Wednesday, 664 US flights had been cancelled by the morning and more than 1,000 had been delayed, according to FlightAware.com  a site that monitors air travel.
The slight warming comes after some truly stunning temperatures - in some cases lower than the surface of Mars. Chicago was colder than the South Pole when officials at the Lincoln Park zoo decided to keep Anana the polar bear inside on Monday. Unlike her cousins in the wild, she had not built up the protective fat stores to insulate herself against the chill.
It was so cold in Kentucky that an escaped inmate begged to be let back into prison.
And more than 500 passengers spent the night aboard trains stranded by snow drifts in Illinois.
The most dangerous cold - cold that can cause frostbite in minutes and death in a matter of hours - hit the Midwest, as a weather phenomenon called the "polar vortex" brought frigid air from the Arctic.
Schools, businesses and government offices were closed. Water mains and household pipes froze. Roads and pavements became ice rinks. The National Guard was called in to help rescue hundreds of stranded motorists.
There were reports of at least 20 deaths caused by the extreme weather. Many were as a result of traffic accidents, but four women were found dead in the snow, including an elderly woman with Alzheimer's disease in New York and a young woman discovered outside her home in the Midwestern state of Minnesota.
Hypothermia was blamed for the death of a man in Wisconsin and was a factor in a death in Ohio, both in the Midwest. And at least four Chicago men suffered heart attacks shovelling snow.