A large part of the United States is preparing for a major outbreak of winter – and severe cold

A blast of arctic air will send temperatures plummeting across the eastern United States this week — and the cold conditions could linger, exposing millions to a prolonged and dangerous bout of winter weather.

“We’re going to be stuck in a cooler pattern,” said Zachary Yack, a National Weather Service meteorologist based in Chicago. “It will certainly go into the middle and early part of next week.”

The arctic outbreak has already caused temperatures to drop in the northern plains. Forecasters predicted Minneapolis’ high temperature would be 20 degrees Fahrenheit on Thursday and drop to 12 degrees Saturday.

In Chicago, high temperatures were expected to hover in the low 20s for the next week. Forecasters in both cities expect overnight temperatures to drop into the single digits.

Yack said a low-pressure system was moving south, pulling arctic air from northern Canada behind it.

Distortions in the jet stream – patterns of strong winds in the upper atmosphere – will allow the cold air to stagnate and linger over most of the eastern United States.

“The jet stream will be centered over the central and southern United States. There’s nothing that’s going to move it back,” Yack said.

Temperatures are expected to remain well below average – even in January.

The system will not be limited to the Midwest and Plains states.

“The coldest air of the season to date and dangerous wind chill is likely over many areas in the Southeast,” The National Oceanic and Atmospheric Administration’s Climate Prediction Center wrote in a long-range forecast. “Below freezing temperatures are possible as far south as the Gulf Coast and much of the Florida peninsula. Impacts to very sensitive citrus crops are possible.”

Snow is possible in the southern Plains states and Southeast, with the potential for heavy snow in the Appalachian Mountains, Ohio Valley, Great Lakes and interior Northeast.

The Climate Prediction Center’s forecast eight to 14 days in advance predicts below-average temperatures for nearly all of the eastern United States, indicating that the system may continue to linger beyond next week.

Yack said he is concerned about people in Chicago who work outside and vulnerable populations, such as those experiencing homelessness.

“You can have subzero chills. It can lead to frostbite for short periods of time,” he said.