Parts of the Northeast are digging themselves out Friday after a powerful nor'easter dumped up to 20 inches of snow in some areas. Now, those same areas are expected to see frigid temperatures through the weekend.
"Very cold temperatures and dangerous wind chills are moving in behind the system," the National Weather Service announced Friday. "Some of the coldest air of the year should arrive by the weekend over the northern tier of the country."
The winter weather forced the closure of all New York City public schools on Friday, and the city's new Mayor Bill de Blasio urged residents to stay home.
"This has been and remains a dangerous storm. It is going to be bitter cold today, and New Yorkers need to be extremely careful going outdoors. The best things people can do are to stay off the roads so we can clear them as fast as possible, and to check in on elderly and vulnerable neighbors who might need help this morning," he said.
Snow piled up in Massachusetts as forecasters predicted Boston could see anywhere from 10 to 18 inches of snow by nightfall.
"This storm presents a different set of dangers," said Massachusetts Gov. Deval Patrick.
Snow and freezing temperatures aren't the only worries in Massachusetts. Coastal residents are also bracing for potential high tides from the winter storm.
"When you have 40- to 50-mile-per-hour winds coming in and the tides, they don't go back out as far, so when you have the second tide come in, it just builds and builds and builds," resident Peter Martin told HLN affiliate WHDH.
In neighboring New Hampshire, road crews are having a tough time clearing roads due to the bitter cold temperatures.
"It's difficult because the frigid temperatures make the anti-icing chemicals somewhat limited in their effectiveness," Bill Boynton, of the New Hampshire Department of Transportation, told HLN affiliate WMUR.
Thousands of flights were canceled Friday due to heavy snowfall and low visibility, stranding thousands of travelers at airports.
The NFL's wildcard playoff weekend could be significantly affected by the winter weather. A snowstorm is expected to move through the Ohio River Valley just in time for Sunday's 1:05 p.m. ET game between the San Diego Chargers and the Cincinnati Bengals.
Later that afternoon, the San Francisco 49ers will face the Green Bay Packers. Forecasters believe the game-time temperature will be about 8 degrees below zero with wind gusts of 15 to 20 miles per hour.
CNN Wires contributed to this report.