Some 160 warming centres were opened in Chicago, where temperatures could potentially equal or exceed the all-time record of -27 degrees Fahrenheit.
The US Postal Service - known for its commitment to bringing the mail whatever the weather - suspended deliveries in parts of Indiana, Michigan, Illinois, Ohio, the Dakotas and Nebraska.
The culprit? A swirl of arctic air that broke away from the polar vortex that usually encircles the North Pole.
This outbreak may break some daily records for cold and is likely to be even more brutal than five years ago, especially with added wind chill, said Jeff Masters, meteorology director of the private weather firm Weather Underground.
Nationwide, 2,700 flights were cancelled on Wednesday while another 1,800 flights scheduled for today have also been called off. These tubes are thin, and if there's any moisture in them when temperatures drop to extreme levels, they can freeze, causing blockages that prevent fuel from flowing.
At the same time, La Crosse, Wisconsin, had temperatures of minus 30 degrees Fahrenheit (minus 34 degrees Celsius) at 5.20 a.m. on Wednesday, said the National Weather Service. If those conditions line up, they could "easily push" temperatures to minus-35 to minus-39 in Northern Illinois, the National Weather Service said Tuesday, which would jeopardize if not topple the state's coldest low.
The wind blows snow over the subway tracks on January 30, 2019 in NY.
Jim Hayes, a National Weather Service meteorologist, warned that frostbite was possible within 10 minutes in the intense cold.
Michigan Governor Gretchen Whitmer said government offices would remain closed through Thursday and nonessential employees would stay home. Nonessential employees would stay home.
The US Postal Service said it would suspend mail delivery on Wednesday in parts or all of several Midwest states including North Dakota, South Dakota, Nebraska, Kansas, Minnesota, Wisconsin, Iowa, Illinois, Indiana and MI.
"The priority must continue to be on keeping people safe", Whitmer said in a statement. "There is a real risk of hypothermia and frostbite". Five city buses were also deployed to serve as mobile warming centers for homeless people, while city police handed out hats, jackets and blankets.
Snow and ice cover the vegetation on the edge of the Horseshoe Falls.
"The concern would be whether they are going to be able to survive in these bitter cold temperatures", Patten told AFP. "You'll have to wait for the weekend, before you see any higher temperatures". "I gotta let you go".
Much of the Chicago River was frozen over.
Remnants of a weekend snowstorm continued to plague portions of the northeast U.S. - with strong winds and blowing snow reducing visibility on roads.
As much as two feet (60 cm) of snow was forecast in Wisconsin, and six inches (15 cm) in IL.