Break out the gloves and hats: the coldest air of the season is slamming the Northeast on Tuesday.
Wind chills -- what temperature it feels like -- plunged below zero in New York City and Boston Tuesday morning, while it could feel like negative 30 degrees in northern New England.
The arctic blast is forecast to continue through Wednesday morning.
Here is your cheat sheet for how to brave the frigid weather, from what to wear outside to what to remember when driving.
This story was originally published in the winter of 2017 - 2018.
How to stay safe outside
Those with prolonged exposure or those not dressed appropriately for the weather are in danger of frostbite and hypothermia, National Weather Service meteorologist Jay Engle told ABC News.
Frostbite results in the loss of feeling and color in affected areas -- usually the nose, ears, cheeks, fingers, toes or chin, according to the U.S. Centers for Disease Control and Prevention (CDC). Frostbite could potentially cause permanent damage and, in severe cases, can lead to amputation, the CDC said.
Someone suffering from frostbite can be unaware of it because tissues that become frozen are numb, the CDC said. These are all signs of frostbite: numbness, white or grayish-yellow skin, or skin that feels unusually firm or waxy.
"Don't rub your hands -- if you have frost-nip or frostbite, rubbing actually causes tissue damage," Dr. Randall Wexler, professor of family medicine at Ohio State University, told ABC News.
If you think you are developing frostbite, "keep the area covered if you can ... because if you have frostbite on your hand and you pull off your glove, you may cause tissue damage," Wexler said.
He added, "That's also when you want to start trying to raise your core body temperature -- get rid of wet clothes, put on clothes that are warm and dry."
There's also hypothermia -- or abnormally low body temperature -- which can impact the brain, "making the victim unable to think clearly or move well," the CDC said. "This makes hypothermia especially dangerous because a person may not know that it's happening and won't be able to do anything about it."
Engle recommends to "dress in three or more layers. One big thick winter coat tends not to do the trick. You have to have a thick sweater underneath and then a lighter jacket on top of that and then your winter coat."
"People really should keep their heads covered because that's where majority of heat gets lost," Engle added.
Wexler said moving can generate heat. But try to avoid sweating.
"If you are overheated and start to sweat, that lowers your body temperature and makes you more susceptible to cold injury," he said. "You want to be able to adjust your layers, zip and unzip."
Wexler also recommended staying hydrated because "dehydration can help promote cold injury."
The young and elderly should be especially careful in the cold.
"Their ability to maintain core body temperature is harder than mid-age and younger adults," he said. "Kids, especially babies, lose a disproportionate amount of heat from their head -- that's why you want to have a hat on their head when you're out there. Older people are more at risk simply because it is more difficult to regulate our core body temperature as we get older."
How to keep your car safe
When the temperature dips, getting behind the wheel can prove to be a challenge. Problems include dead car batteries, iced-over windshields, broken car locks and driving with no traction.
Audra Fordin, founder of Woman Auto Know and the owner of Great Bear Auto Repair in Queens, New York, provided these tips:
1. Before you hit the road, check under the hood.
"If it's really cold outside, you want to make sure that your battery is going to be good in the freezing cold weather," Fordin said. "If you see any snow or blue stuff that's growing off your battery, that's an indication you want to go to the shop to have your battery checked."
2. Iced out windshields? Turn to your wallet for help.
"If you get to your car and can't see, pull out a credit card, and you can just wipe that frost away," Fordin said.
3. Fighting a stubborn car lock? Get sanitizing.
"If your lock is frozen, put the sanitizer on the key, and then put the key into the lock," Fordin said.
4. If your car can't gain traction, let your floor mat give an assist.
"Grab your floor mat, you're going to put it underneath the wheel," Fordin said. "That will give you enough traction to pull your car out and hit the road."