There's cold, and then there's Arctic cold — and multiple major cities across the United States are about to experience the latter.
A frigid cold front is expected to hit dozens of states across the Midwest and mountain regions over the next 72 hours, promising to turn Monday's work-related foot traffic into a scene from March of the Penguins.
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The cold front, which is predicted to bring temperatures between 20 and 40 degrees lower than average in states that already experience harsh January weather, is coming down from the polar regions above northern Canada. The pocket of cold air, called a "polar vortex," was blocked up north by a high-pressure area that meteorologists refer to as a "ridge," according to Mark Ressler, senior meteorologist at The Weather Channel.
The ridge has high pressure on both the surface level and aloft, meaning miles above the Earth's surface. The ridge was formed by pools of warm water that have collected near the Gulf of Alaska, according to Joe D'Aleo, co-chief meteorologist at WeatherBELL Analytics. These pools of warm water, which are up to seven degrees warmer than normal, heat the surrounding air and expand it, raising the temperature and pressure, and block air from the Pacific Ocean as it tries to move eastward into Canada.
A pool of warm water gathers near Alaska creating a pressurized ridge. Image: WeatherBELL Analytics
This allows air from the Arctic to sit undisturbed in northern Canada, becoming colder and colder before flowing "like molasses" down south through Canada and into the United States, D'Aleo explained. In some places, the weather will be colder than it's been in 20 years.
This same high-pressure ridge has been responsible for other odd weather patterns over the past few months, including a draught that has been plaguing Northern California, Ressler said. In San Francisco, for example, just over two inches of rain fell in the past six months; that's less than one third of the normal average, The Wall Street Journal reported.
US will soon learn meaning of “polar vortex” as record cold descends on Midwest Monday. http://t.co/nHR2UuUopE pic.twitter.com/o1jwgp0uGC
— Jim Roberts (@nycjim) January 4, 2014
The most extreme temperatures are expected to hit major U.S. cities on Monday, with the high temperature in Chicago expected to be -10 degrees Fahrenheit, according to D'Aleo. States in the northern plains and upper Midwest regions (i.e. North and South Dakota, Minnesota and Wisconsin) are expected to be hit hardest, Ressler said.
This cold air is not the only weather Americans should be wary of this weekend. The subzero temperatures are expected to hit after winter storm Ion is done pounding the Ohio Valley and Great Lakes regions with snow. The polar vortex may actually be worse than it would otherwise be following Ion and winter storm Hercules. These two snowstorms that have hit the mountain west, Midwest and northeast regions have built up the snowpack, which should help maintain the frigid temperatures of the polar vortex, Ressler said.
The extreme weather is causing emergency alerts, possible school closings and will likely play a part in the NFL playoffs. (The Green Bay Packers host the San Francisco 49ers on Sunday, with the city expected to get wind chill that could drop to as low as -51 degrees Fahrenheit.)
Here's a look at how this week's upcoming cold spell will impact regions across the U.S.:
This is the area of the U.S. that will likely be hit the hardest, Ressler said. Minnesota Governor Mark Dayton already canceled all K-12 public schools statewide for Monday in anticipation of the cold weather. In North Dakota, Governor Jack Dalrymple is leaving the decision up to individual districts, but urged superintendents to remember that “keeping students safe is the first priority."
The National Weather Service is predicting wind chill in the South Dakota plains to hit between -40 and -50 degrees Fahrenheit on Monday, and issued a "wind chill warning" to citizens reminding them that frostbite and hypothermia are possible with temperatures that cold. Heavy snow is expected to fall in St. Louis, Mo. on Saturday night and into Sunday, and wind chill may be as low as -25 degrees Fahrenheit on Monday.
A lot of attention in this region will be focused on one specific location: Lambeau Field in Green Bay, Wisc., where the Packers are scheduled to host the 49ers Sunday afternoon in the first round of the NFL playoffs. The team finally sold out the nearly 73,000-seat stadium on Friday, meaning its faithful fans will be cheering on the Pack in wind chill that could reach as low as -51 degrees Fahrenheit, according to Sports Illustrated. (The temperature for Niners fans in San Francisco on Sunday: 66 degrees Fahrenheit and sunny.)
Another playoff game between the Cincinnati Bengals and San Diego Chargers Sunday morning is expecting temperatures right around freezing at kickoff. Chargers defensive back Richard Marshall tweeted out the following picture of his team's practice ahead of the game on Saturday morning.
Got to love this football weather #practice pic.twitter.com/c3FSAYpLMY
— Richard Marshall (@TheMarshall31) January 4, 2014
The other major focus in this region is Chicago, which is expected to get another six inches of snow between Saturday and Sunday before subzero temperatures linger throughout the day Monday. In Indianapolis, trash pickup has been canceled on both Monday and Tuesday.

New Yorkers were greeted with snow from winter storm Hercules on Friday, and after temperatures are expected to rise slightly on Sunday and Monday, Tuesday temperatures could be as low as single digits in Manhattan. Boston had a similar experience Friday, and meteorologists expect the temperature to reach zero degrees Fahrenheit Saturday night. The city's record low was -4 degrees Fahrenheit back in 1981.

Snowfall led to school closures in both Virginia and Washington, D.C. on Friday, and areas of the capital are expected to have temperatures in the single digits on Monday.
As bad as the storm and cold weather will be over the next 72 hours, things will break, according to D'Aleo. "It's only going to be a two or three day siege," he said. "But it will be very harsh for those few days."
Citizens living in states where cold fronts are expected to hit are encouraged to stay indoors, if possible, and wear multiple layers if forced to venture outside. Hypothermia can start impacting people as soon as the temperature drops to 50 degrees Fahrenheit, which means temperatures over the next few days could put people at risk.
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Image: Spencer Platt/Getty Images, Darren McCollester/Getty Images