It’s going to be bitter cold.

With an intrusion of Arctic air arriving early morning Saturday, look for a steady drop in temperatures during the day, heading down from the high teens to about 12 degrees by late afternoon, forecasters say.

With northwest winds of 15 to 25 mph, and higher gusts, conditions will feel more like the negative single digits, said Faye Barthold, a National Weather Service meteorologist based in Upton. There’s also a slight chance for snow showers.

Then, the really bitter cold sets in, with a wind chill advisory in effect for Long Island from 4 p.m. Saturday through noon Sunday, warning of “potentially dangerous” conditions.

Air temperatures could head down early Sunday to 1 degree or so — which could break the record low for the day of 7, set in 2015 at Long Island MacArthur Airport.

There’s more. With gusts as high as 35 to 45 mph, wind chill gets added into the mix, with overnight feels-like temperatures of about minus 18 to minus 20 degrees for Long Island.

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With such potentially “life-threatening” conditions, the weather service warns that with “cold spells of this magnitude,” frostbite and hypothermia are risks for those who don’t take precautions. Especially vulnerable are the elderly and babies in locations with inadequate heat, and the homeless and others who remain outdoors.

If you must venture outdoors overnight Saturday into Sunday, know that the wind chill could result in frostbite in less than half an hour, the weather service said. Also, there’s potential for pipes to freeze and overworked furnaces to conk out, meaning no heat or running water.

“For anyone without heat, especially the homeless, this kind of weather is potentially deadly,” said News 12 Long Island meteorologist Bill Korbel. “And don’t forget about pets. They are not immune to the cold.”

During the frigid blast, Long Island Rail Road waiting rooms will stay open round-the-clock through Monday afternoon, so passengers can have shelter from the cold, the railroad said.

As Sunday’s temperatures later climb to possible highs in the mid-teens, another record could fall by the wayside, that of the day’s coldest high temperature, 26 degrees, set in 1987.

If there is any bright side, it’s that this cold is “quick-hitting,” unlike last February, which saw a steady stream of single-digit days, Barthold said.

Rain, starting as snow, is expected for Monday — with highs in the mid-30s — into Tuesday night. Tuesday’s expected high? About 50 degrees.