That’s the advice from weather forecasters, who say this year’s picturesque white Christmas will be followed by an ugly onslaught of bitter cold in New England through New Year’s Day and beyond.
Temperatures will likely peak Tuesday at 27 degrees, Wednesday at 21 degrees, and Thursday at only 13 degrees. Low temperatures will drop into the low single digits. Add in the wind chill and it will feel like it’s as cold as minus-10 degrees at some points over the coming days.
Outside of Boston, temperatures and wind chills are expected to be even worse.
To protect yourself against such harsh conditions, the weather service suggests wearing at least two upper-body layers in cold, and three or more in extreme cold. One to two layers of pants could be sufficient in cold, while two or more pants layers are suggested in the extreme cold.
Waterproof boots, gloves, a warm hat, and an outer layer to protect against wind and snow are also recommended. In extreme cold, the weather service advised those traveling outdoors to wear a face mask.
There is no exact technical definition of extreme cold, said Robert Oravec, the lead forecaster for the National Weather Service Weather Prediction Center in College Park, Maryland. But the term can be loosely applied to conditions when temperatures are well below freezing and the danger of frostbite is high.
Forecasters suggest layering up even if you only expect to be outside a short time.
“Frostbite doesn’t take long,” Bill Simpson, a meteorologist in the Taunton office of the weather service, said. “First the skin goes red, and then the worst thing is if it starts going white.”
“As best you can, cover up all skin surfaces,” he said.
“If you’re heavily bundled up, it’s not that bad because your body is retaining that heat,” he said.
Simpson said that simply wearing lots of clothing may not be enough, though, as ineffective layering can still leave the body exposed to the cold.
He said that people should make sure to dress for warmth not for looks. Otherwise, he said, “Your body will start pulling blood to the vital organs and the first thing to go is the fingers and toes.”
Simpson said morning commuters Wednesday and Thursday should try to wear face masks and hats, if possible.
“You lose a surprising amount of heat from your head, so wearing a hat is always advised if you can’t wear a mask,” he said. “It’s going to remain well below freezing into next week at the earliest.”
Looking ahead to the weekend, Simpson said Bostonians celebrating New Year’s Eve should brace themselves. The low that night is expected to be 5 degrees.
“For First Night, if you can in this extreme cold, cover all skin surfaces,” he said. “Winter is with us for at least a week to 10 days, with much below normal temperatures.”Globe correspondent Alyssa Meyers contributed to this report. Ben Thompson can be reached at firstname.lastname@example.org. Follow him on Twitter @Globe_Thompson. Alyssa Meyers can be reached at email@example.com. Follow her on Twitter @ameyers_.