(NewsNation) — Extremely cold weather hit New England this weekend, with what forecasters called “once-in-a-generation” wind chills.

The National Weather Service on Saturday morning said dangerously cold wind chill temperatures will continue in the Northeast through the evening. In Northern Maine, blizzard conditions are expected.

Temperatures are slated to be 10 to 30 degrees below average over parts of the Northeast into the coastal Mid-Atlantic, the NWS said.

“High winds may bring power outages, tree and property damage, and difficult travel over the northern Rocky Mountain Front and adjacent High Plains through Saturday afternoon,” the NWS said. “Heavy snow will move into the Sierras of California Saturday.”

In New York, according to Poweroutage.us, more than 9,600 people were without power around 9:30 a.m. Saturday.

At 3 a.m. Saturday on Twitter, the National Weather Service in Boston shared a picture of wind chills between -30 and -40.

“We are past the peak of the cold. Temperatures will gradually moderate to above normal temperatures by tomorrow afternoon across the region,” NWS said in a later tweet. “Nonetheless, still a few more hours of dangerous wind chill temperatures.”

As the National Weather Service in Caribou, Maine, pointed out, wind chills of -50 to -60 degrees can cause frostbite in just minutes.

Boston declared a “cold emergency,” and public schools in the city were closed Friday, Axios reported, because of the polar vortex. According to Axios, this is a tropospheric polar vortex.

Axios said temperatures should moderate by Monday.

“Cold high pressure over the Mid-Atlantic and northern New York State will move eastward off the East Coast by early Sunday,” The National Weather Service predicted.

The Associated Press contributed to this report.