Temperatures in Chicago could drop to an astounding -25 degrees by Tuesday night, the National Weather Service said.

(Reuters) ― A blast of super-cold arctic air is bringing dangerous sub-zero cold to the U.S. Midwest and Northeast as the system cartwheels through the Dakotas into Chicago, Illinois, and on to New England.

By Tuesday night and into Wednesday morning, Chicago will hit an astounding 20-to-25 below-zero Farhenheit, the National Weather Service said.

“This is dangerous, deadly cold,” said Richard Bann, meteorologist with the NWS’s Weather Prediction Center in College Park Maryland. “Exposed skin loses heat fast, like you don’t even know.”

Blizzard conditions are predicted across parts of the western Ohio Valley and snow is expected Tuesday through Wednesday from the Great Lakes area into New England, the weather service said.

“Most of the snow will be in the Dakotas, the Twin Cities and Central Michigan, where they might get a foot or more,” Bann said. “Upstate New York, Vermont and New Hampshire will see less than a foot. Boston and cities in the east will get less than an inch.”

“But it’s going to be cold throughout the east coast,” he said. “Even parts of Mississippi and Alabama might see an inch or two of snow before this is over.”

But Chicago will take the main brunt of the super-cold weather.

“An entire generation has gone by without experiencing this type of cold in the Chicago area.” said Mike Doll, a senior meteorologist at AccuWeather.

Frigid temperatures were already affecting parts of northern Minnesota and northern Wisconsin. The mercury dipped to minus 44 degrees Fahrenheit (minus 42 Celsius) in International Falls, Minnesota, on Sunday morning, breaking the previous record by 8 degrees, the NWS said in a tweet.

The agency’s Des Moines branch said “dangerous, life-threatening cold air” will impact Iowa from Tuesday morning through Friday morning, with wind chill values on Wednesday likely to range from minus 45 Fahrenheit to minus 55 Fahrenheit across the northern part of the state.

Delta Airlines said it would waive change fees for passengers affected by the winter weather in Chicago, Detroit and areas of the Upper Midwest.