The National Weather Service said the mercury will start dipping Saturday, but the coldest air would not arrive until Sunday morning — with several cities facing the prospect of subzero temperatures.
"For people stepping outside on Sunday morning, it's going to be like walking into a freezer," said Weather Channel Lead Forecaster Michael Palmer. "This will be the coldest air for more than a decade for much of the Northeast."
Boston's forecast low of 2 below zero looked relatively balmy compared to the outlook for 9 below zero in Hartford, Connecticut. Albany was forecast to experience 10 below zero, with 11 below possible in Worcester, Massachusetts, according to The Weather Channel.
Let our news meet your inbox. The news and stories that matters, delivered weekday mornings.
While New York City was not expected to see sub-zero temperatures, the forecast for Saturday night is a frosty 1 degree, according to the National Weather Service. That would match the coldest temperature in New York City this century. It hasn't sunk to zero since Jan. 27, 1994.
An Ice Festival, featuring live ice carving, scheduled for Saturday in Central Park was even canceled, ironically because of the expected cold, according to festival officials.
“New Yorkers should take this weather very seriously,” said New York Mayor Bill de Blasio. “These are not temperatures we see often.” The mayor activated “Code Blue” status, which mobilizes the Department of Homeless Services to lead an “aggressive outreach effort” to make sure the city’s homeless are off the streets.
Meanwhile, the New York City Department of Buildings advised property owners to secure cranes, as winds were forecast to gust at 45 mph. A crane in the city collapsed last week, leaving one person dead, but it was unclear if wind caused the catastrophe.
Boston, Philadelphia, Washington, D.C., Hartford, Connecticut, and Albany, New York, also have the potential to set records over the weekend.
The Massachusetts Bay Transportation Authority warned that trains might be stalled because of mechanical issues caused by the cold. And the U.S. Coast Guard urged the Massachusetts and Rhode Island fishing flees to take extreme caution out on the water.
Wind chills are expected to plummet 20 to 40 degrees below zero across the region, with the National Weather Service issuing a patchwork of warnings and watches. It said conditions "will result in frostbite and lead to hypothermia or death if precautions are not taken."
Blame the bitter cold on the polar vortex, a large cyclone that sits above the North Pole all year round. A "piece" of this weather system has broken off and traveled south, Palmer said.
The Midwest will feel the chill on Friday — with forecast lows of 7 below zero in Green Bay, Wisconsin, and 2 below zero in Chicago. The icy blast will move through the Great Lakes on Friday night and into the Northeast on Saturday.
That will be followed by a snowstorm that is forecast to move through the Midwest on Sunday and into the Northeast on Monday — although meteorologists say it is too early to predict the storm's exact path or power.
While the East is likely to be locked in a freezer the whole weekend, things will be balmy out West with temperatures in 80s and 90s in California, Arizona and elsewhere, according to forecasters.
Corky Siemaszko is a senior writer for NBC News Digital.
Alexander Smith is a senior reporter for NBC News Digital based in London.
Elisha Fieldstadt is a breaking news reporter for NBC News.