The National Weather Service has said that a “significant Arctic outbreak” of cold air will cover large swathes of the United States starting this weekend, with frigid conditions anticipated to last well into mid-January.

Winter storms are also expected to follow in the wake of the plunging temperatures.

Temperatures are forecast to plummet below average for much of the nation, with the most severe cold gripping areas east of the Rocky Mountains and reaching as far south as the Gulf Coast and Florida. Dangerous wind chills are likely across many areas of the Southeast, too.

“This will likely be the most significant cold we have seen in years,” said forecasters at the National Weather Service office in Wakefield, Va., adding that the bout of below-normal temperatures “is likely to prevail into mid-January.”

This Arctic outbreak is expected to bring a sustained period of cold weather across the northern Plains, Great Lakes, Midwest and East Coast as well.

Snow and ice are predicted, too.

The Weather Prediction Center has also warned that a winter storm will begin in the Central Plains on Saturday night. Heavy snow and significant icing are expected to spread east, potentially affecting the Mid-Atlantic by early next week.