Temperatures across the northeastern US fell drastically overnight on Saturday, with wind speeds rapidly increasing, as the region faced some of the coldest wind chills in decades.

Frigid conditions were expected to break records across the region. As of early Saturday, it was -15° Celsius in New York City, -21° in Hartford, Connecticut, and -26° in Concord, New Hampshire, with the wind making it feel much colder everywhere. The wind chill reading in Caribou, Maine, was -41° Celsius.

Conditions across the region were expected to quickly become more moderate by Sunday. In the meantime, government officials opened warming shelters, urged people to stay inside and prepared for the possibility of widespread power outages. Early Saturday morning, more than 10,000 customers across New York State were without electricity.

Wind chill is a measurement to describe the combined effects of sustained winds and low air temperatures on exposed skin. It begins to become dangerous around -31° degrees Celsius.

“This is one of the coldest events that we’ve seen in years,” said Samantha Sheehan, a spokeswoman for Miro Weinberger, the mayor of Burlington, Vermont. “We’re encouraging people to stay indoors.”

The core of the Arctic air mass is over northern New England, where residents pride themselves on cold-weather endurance. But the combination of frigid cold and high winds forced some to make rare accommodations.

Ninety six kilometres to the south, at Lake Waukewan in Meredith, North Hampshire, organisers opted not to cancel the Pond Hockey Classic, a packed schedule of outdoor ice hockey games for die-hard adult players.

Organisers warned players of the risk of frostbite and hypothermia and urged them to bring dry clothing, to leave immediately after their games.

In Boston, where the deep freeze hit -22° Celsius in the early hours of Saturday, governor Maura Healey of Massachusetts said the doors at South Station, the downtown train hub, would remain unlocked on Saturday.

In New York, a Code Blue was in effect, meaning that no one seeking shelter would be denied.