You know it's going to be cold when the National Weather Service hoists wind chill advisories and warnings from North Dakota to Maine. These areas are accustomed to cold, but even so, the prediction of dangerous conditions — with wind chills of at least minus-30 degrees Fahrenheit, and possibly as low as minus-45 degrees — is impressive.

The worst of round one of the cold is hitting the Plains and Midwest on Wednesday and Thursday before rotating eastward to the Mid-Atlantic and Northeast on Thursday and Friday.

SEE ALSO: Climate scientists vow to stand up to Trump

A storm system will race along the dividing zone between milder air to the south and Arctic air to the north into the early weekend, spreading a messy mix of snow, ice and rain from Chicago to New York and Boston.

In the Midwest, round two will come roaring in for the weekend. First, however, we need to deal with the nearer term.

In Chicago, high temperatures on Thursday are predicted to hold in the single digits above zero Fahrenheit.

Rockford, Illinois, is expected to set a record cold daily high, beating the current record of 9 degrees set in 1932. According to the National Weather Service, the last time a high of under 10 degrees Fahrenheit took place on or before Dec. 15 was in 2009.

The National Weather Service forecast office in LaCrosse, Wisconsin has this to say about the cold wind chills forecast for Wednesday night and Thursday:

"Take precautions to protect yourself and your pets from the cold. Limit outdoor exposure. Bundle up and dress in layers."

The weather service issued a wind chill advisory Wednesday for all of North Dakota, Minnesota, Wisconsin, and parts of Montana, Wyoming, South Dakota, Iowa, Illinois, Indiana, Ohio and Pennsylvania. Wind chill watches are up for parts of New York, Vermont, New Hampshire and Maine, as well.

Computer model projection of wind chills on Friday morning in the New York City area. Image: weatherbell analytics

Along the East Coast, this visit by the polar vortex will be like a houseguest who comes into your home, leaves stuff everywhere, turns the place upside down, and inexplicably leaves before they were originally intending to do so.

The cold in the East is going to be intense, but brief. And unfortunately, the visit will include a standing invite to come back again, perhaps several times, during this winter.

Or, to put it another way, like so much of what's happened during 2016, the weather this winter is poised to punch you in the face, repeatedly.

Most intense cold hits East Coast on Thursday and Friday

The most intense cold will hit the big cities from Washington to Boston on Thursday and Friday. The cold will be accompanied by strong, possibly even damaging, winds, especially on Thursday night as an Arctic cold front passes through the area.

New Yorkers will wake up on Friday to temperatures of between 9 and 14 degrees Fahrenheit and winds gusting above 30 miles per hour, making any exposed skin painful after just a few minutes outdoors.

Like so much of what's happened during 2016, the weather this winter is poised to punch you in the face, repeatedly.

Temperatures on Friday will not get out of the 20s in Washington and New York, and parts of New England could be stuck in the single digits to teens Fahrenheit.

Wind chills approaching 15 to 30 degrees below zero in parts of New England will mean that this is the coldest air since at least Valentine's Day last year.

However, it is unlikely that there will be widespread toppling of cold temperature records. While this is a formidably cold air mass, it's not the middle of January into early February, when temperatures tend to dip even more.

Polar vortex is just saying hello, in its own way

Both of these Arctic blasts are the result of pieces of the polar vortex pinwheeling out of Canada, bringing the coldest air in years to tens of millions of people.

The main polar vortex is a circulation of air enveloping a near-permanent area of low pressure that exists in the upper atmosphere, above typical cruising altitudes for commercial jetliners, over the Arctic.

When these winds weaken, as has been happening recently, filaments of the vortex can break off, and meander south into the U.S., Europe and parts of Asia.

In November and December, parts of the vortex set up over Siberia, causing exceptionally cold and snowy conditions there while driving unusually mild air into the Arctic and melting sea ice.

Second blast takes aim at Midwest, again (sorry)

Although the East Coast will see moderating temperatures after a storm system moves through during the weekend, another surge of Arctic air will pinwheel into the Upper Midwest at that time. This will bring more bone-chilling cold to Minneapolis, Des Moines and Chicago.

Computer model projecting high/low temperatures for Chicago during the next two weeks. Image: Weatherbell analytics

In fact, many locations in Minnesota, Wisconsin, Illinois, Iowa, Nebraska and the Dakotas may not see temperatures rise above about 32 degrees Fahrenheit for at least two weeks, which is an impressive, though not remotely unheard of, occurrence for those areas.

The second cold blast may dig farther south than the first one did, based on computer model projections. It will be similar in intensity.

In Bismarck, North Dakota, for example, the forecast high temperature on Saturday from the National Weather Service is minus-10 degrees Fahrenheit, with an overnight low early Sunday morning of about minus-22 degrees.

Chicago is forecast to have a high of just 10 degrees on Sunday, with a low of minus-3 degrees that night into Monday morning. Areas just outside of downtown could see temperatures plummet into the minus-teens Fahrenheit on Monday morning, with wind chills even colder.

Computer models are projecting that this cold air will swing east again with time, but that it may moderate as it does so.