The subzero temperatures seized large parts of the Northeast and the Midwest, where as many as 75 million Americans live. By Wednesday night, 85 percent of the U.S. land area and 230 million Americans will have experienced freezing temperatures, forecasters said.
Chicago's temperature fell to 15 degrees below zero. Fargo, North Dakota, hit minus 31 degrees. Minneapolis reached minus 27 degrees. As of 1 p.m. CT (2 p.m. ET) Wednesday, it was 0 degrees in both Cleveland and Buffalo, New York.
"Historic cold, unprecedented cold, these are all adjectives you could use to describe this," Kathryn Prociv, a meteorologist for NBC News, said.
"These are some of the coldest temperatures an entire generation has ever felt, talking about the millennials," Prociv said. "A lot of these temperatures will be the coldest since about 1994, when a lot of them were just being born."
The U.S. Postal Service said it would suspend delivery services Wednesday in Chicago, Minnesota, western Wisconsin, Iowa and western Illinois. There will also be no mail or package pickups, it said.
"You're talking about frostbite and hypothermia issues very quickly, like in a matter of minutes, maybe seconds," said Brian Hurley, a meteorologist with the NWS' Weather Prediction Center.
For emergency responders, such conditions are life-threatening but a part of the job.
When any equipment gets wet, it "freezes to the ground," Rochester fire Capt. Greg Neumann said.
"Even the hose lines get froze up," Neumann told NBC affiliate KTTC. "They grab the snow, so everything is three times heavier than they actually are."
But in Kentucky, Gov. Matt Bevin complained that people just aren't tough enough. In an interview with WHAS radio of Louisville, Bevin said he wasn't happy that dozens of school districts were canceling classes Wednesday.
"Now we cancel school for cold," Bevin told host Terry Meiners. "I mean, there's no ice going with it or any snow. What happens to America? We're getting soft, Terry. We're getting soft."
Bevin said that he was being "only slightly facetious" and that he had a real concern — "that in America, on this and any number of other fronts, we're sending messages to our young people that if life is hard, you can curl up in the fetal position somewhere in a warm place and just wait 'til it stops being hard. And that just isn't reality."
(You can listen to the entire interview here.)