BOSTON (AP) — Arctic air descended into the Northeast on Saturday morning, bringing dangerously cold sub-zero temperatures and wind chills that dropped to minus 45 to minus 50 degrees Fahrenheit (minus 43 to minus 45 C) in many areas.

Atop Mount Washington in New Hampshire's White Mountains, the overnight wind chill was measured at minus 108 degrees F (minus 78 C), according to the weather observatory at the peak of the Northeast's highest mountain, famous for its extreme weather conditions.

“This is just kind of an Arctic intrusion," said Stephen Baron, a meteorologist with the National Weather Service in Gray, Maine. “Sometimes in the winter the Jetstream dips and the Arctic oscillation allows the cold air to come into our area for a day or two.”

Friday's high winds were blamed for the death of an infant in Southwick, Massachusetts.

The winds brought a tree branch down on a vehicle driven by a 23-year-old Winstead, Connecticut, woman, according to a statement from the Hampden district attorney's office.

The driver was taken to the hospital with serious injuries, but the infant died, authorities said.

Most people heeded warnings to stay inside on Saturday, but some people had little choice but to go out.

Gin Koo, 36, braved the cold to take his Boston terrier, Bee, out for a necessary walk.

“I can't remember it being this cold, not since 2015," said Koo, who was wearing three shirts and a down jacket, as well as a hat and a hood. Bee still shivered despite his doggie coat. “I wouldn't go out if I didn't have to."

Paul Butler, 45, who has been homeless since he was evicted in December 2021, took shelter in South Station, the Boston transit hub that authorities kept open overnight so unhoused people had somewhere warm to stay.

Boston, like many communities, opened warming centers.

“This is the coldest I ever, ever remember, and I worked the door at a bunch of clubs for 15 years," said the former Marine, who carried two bags with extra clothes and blankets.

According to the National Weather Service, the following cities set record lows for Feb. 4 on Saturday: Boston; Providence, Rhode Island; Hartford, Connecticut; and Worcester, Massachusetts. The minus 10 degrees Fahrenheit (minus 23 C) temperature in Boston smashed the previous Feb. 4 record of minus 2 set in 1886. The minus 13 degrees (minus 25 C) temperature in Albany, New York, tied the record low for the date. Glens Falls, New York, set a record low of minus 24 degrees (minus 31 C), colder than the previous record of minus 22 set in 1978.

The extreme cold curtailed some traditional winter activities. Ski areas scaled back operations, while in New Hampshire, organizers of an annual ice castle attraction in North Woodstock shortened the evening visitor schedule for Friday and Saturday nights.

Erin Trotta of Massachusetts, who had already booked a visit on Saturday afternoon, still planned to go, but was taking extra steps to stay warm.

“We are prepared to take on the polar vortex ice castles. ... Snow pants, thick winter coats, hand and foot warmers, face masks, the kind where only your eyes are exposed, and good gloves and winter boots. Plan to drink some hot cocoa to keep warm."

In New York’s Adirondack Mountains, Old Forge recorded a temperature early Saturday of -36 degrees. Temperatures plunged into the negative teens in dozens of other cities and towns, with wind chill making it feel even colder. Peak winds late Friday exceeded 50 mph (80 kph) in some areas.

Mackenzie Glasser, owner of Ozzie’s Coffee Bar in Old Forge, said frigid temperatures are just part of living in the Adirondacks.

“I even had customers for the first hour that I was open, and I wasn’t expecting that at 7 a.m. So I don’t think it’s keeping too many people away,” she said.

The good news is that the cold air is expected to move out of much of the region by Sunday, when temperatures could rise to the 40s.

“That's quite a change,” the National Weather Service's Baron said.

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Michael Hill in Albany, New York and Kathy McCormack in Concord, New Hampshire contributed to this story.