A prolonged period of bitter cold will be moving through many parts of the country as 2017 comes to an end. (Claritza Jimenez/The Washington Post)

New Year’s Eve partygoers best bundle up.

As 2017 turns to 2018, the most frigid New Year’s weather in decades will infiltrate the eastern two-thirds of the nation.

The latest and most potent in a series of Arctic blasts is set to crash into the north central United States on Saturday and reach the Eastern Seaboard on Sunday. The blast will uncork piercing cold that will cover enormous territory by Sunday night. From Billings to Boston in the north and from Oklahoma City to Washington to the south, temperatures will average 15 to as many as 50 degrees below normal.

American (GFS) model forecast temperature difference from normal at 1 a.m. Jan. 1. Note these are temperature deviations from average, not actual temperatures.

The temperature averaged over this zone will plummet to a bone-chilling 15.9 degrees just after midnight Jan. 1, signifying the coldest start to the new year in 70 years of records, according to Brian Brettschneider, a climatologist based in Alaska, who ran the numbers.

Temperature forecast just after midnight Jan. 1, 2018, compared to past years back to 1948. (Brian Brettschneider)

New York City will ring in the New Year with an air temperature near 10 degrees and wind chills of zero to minus-5. This would rank among the coldest ball drops in the Big Apple in recorded history. The last time it was so cold was in 1962; 1917 marked the coldest ball drop, when the air temperature was a mere 1 degree.

American (GFS) model forecast of temperatures at 1 a.m. Jan. 1.

But the most extreme cold will focus in the Upper Midwest. Minneapolis may ring in the new year with air temperatures around minus-10 and the wind chill factor close to minus-30.

The National Weather Service predicts an average low temperature of 10 degrees over the entire nation Jan. 1, with about a third of the nation below zero.

National Weather Service low temperature forecast for Jan. 1. (WeatherBell.com)

Here are the predicted high and low temperatures on New Year’s Day for a select group of cities in the grips of this cold wave:

  • Minneapolis: High: 3, low: minus-14
  • Milwaukee: High: 6, low: minus-2
  • St. Louis: High: 13, low: minus-2
  • Oklahoma City: High: 22, low: 11
  • Dallas: High: 30, low: 21
  • Chicago: High: 3, low: minus-10
  • Detroit: High: 10, low: minus-7
  • Cleveland: High: 9, low: minus-1
  • Indianapolis: High: 2, low: minus-11
  • Memphis: High: 24, low: 13
  • Boston: High: 11, low: minus-2
  • New York: High: 20, low: 5
  • Pittsburgh: High: 16, low: 3
  • Washington: High: 23, low: 10
  • Raleigh, N.C.: High: 28, low: 18
  • Atlanta: High: 33, low: 20

Although it may be tempting to question global warming when temperatures are so frigid, the abnormally cold weather over the eastern U.S. and parts of Canada is an anomaly compared to conditions over the rest of the world. Most locations are presently experiencing weather that is considerably warmer than normal.

It is also worth remembering the following:

  • The three warmest years on record globally, since records began in the late 1800s, are 2014, 2015 and 2016.
  • 2017 is expected to rank among the top five warmest years on record.
  • So far this year, warm weather records have outpaced cold by a factor of 3 in the United States.

Much colder than normal weather is expected to continue in the eastern United States for much of the first week of the new year. In Boston, high temperatures may not reach freezing for another 10 days.

The cold snap has been impressive for both its intensity and duration. The bitter chill first arrived around Christmas Eve and has only dug in, trending more frigid over time, breaking records from the Upper Midwest to the Northeast:

The persistent cold is related to a stuck weather pattern, in which the jet stream is bulging north over the northeast Pacific and Alaska, transporting record warmth to that region. Like a seesaw, it is then cascading south near the Rocky Mountains, allowing bitter cold to spill into eastern North America.

Five-day average weather pattern forecast by European model at high altitudes Dec. 31 to Jan. 4 portraying warm-West cold-East temperature configuration. (WeatherBell.com)

The resulting warm-West cold-East temperature configuration is referred to by scientists as the North American winter dipole. Researchers have found this pattern becoming more frequent in recent decades and have related the trend to declining sea ice in the Arctic due to climate warming.