People walk along the High Line in the Manhattan borough of New York, Feb 14, 2016. Temperatures dipped to well below freezing on Sunday with meteorologists dubbing the weather phenomenon as being a polar vortex. [Photo/Agencies]

In Cambridge, Massachusetts, Kristen Carlson, 25, and her boyfriend Ross Crory, also 25, were adapting their plans.

"We're going to brunch," Carlson said. "We're going rock climbing later. Indoor activities. Tonight we're staying in and cooking dinner."

Others embraced the extremes, with more than 2,000 taking part in the Sea Isle, New Jersey, annual "Polar Bear Plunge," dipping into the icy Atlantic to raise funds for the city's revitalization.

Police throughout the region sought homeless people to urge them to spend the night in shelters, where cots, mats and even chairs were rolled out to give people a place to shelter from the cold.

But Kevin Taylor, a 49-year-old native of Massachusetts living on the street in Harvard Square, outside Boston, said he had coped with the cold on his own.

"I got a sleeping bag sized tent that protects me from wind and snow. I got a zero degree sleeping bag and fleece blankets," Taylor said. "I was born and raised in New England. I'm used to this. It'll start breaking tomorrow."

Forecasters said temperatures around Boston would rise to about 29 degrees Fahrenheit (-1.7 Celsius) on Monday.