The first round of cold air has arrived, and it's absolutely freezing in the Northeast. 

Vallee said the first round of cold air is an appetizer for what's to come early next week. He noted in his forecast below that, temperatures across the Midwest and Northeast could be on "average 20-30°F below normal." 

"A very cold air mass will penetrate the Midwest and Northeast U.S. into early next week. As a strong cold front moves through the Plains and Midwest Monday into Tuesday, temperatures will average 20-30°F below normal, leading to potential record cold high temperatures only in the 10s and 20s.

The cold will move into the eastern U.S., including the major cities in the Northeast by Wednesday and Thursday. High temperatures in New York City may fail to escape the 30s Wednesday. Temperatures into the 8-14 day continue to favor colder than normal temperatures in the eastern U.S," Vallee stated.

The second wave of Arctic air is expected to move through the northern Plains and upper Midwest Sunday, into the southern Plains and Ohio Valley Monday, then into the East Coast by Tuesday.