The National Weather Service issued a cold-weather advisory for Chicago and other parts of the state this weekend, warning of “dangerously cold wind chills” that could dip as low as 20 to 25 degrees below zero.

A piece of the polar vortex is spilling into the Midwest, creating extreme cold for the Chicago area and northwest Indiana for the next few days.

Temperatures will plunge into the single digits by early Sunday, and likely won't rise above the single digits until Wednesday.

Chicago area temperatures are predicted to peak in the lower 40s Friday before falling to minus 7 Tuesday, according to the National Weather Service. Meteorologist Casey Sullivan said Friday’s highs will be above normal but won’t be unusual for mid-January.

Temperatures will drop into the single digits and negatives starting Saturday through early next week. Chicagoans should wear lots of layers and limit time outdoors.

Chicago faces cloudy skies and potential snow with risks of slick travel conditions and a plunge in temperatures by the weekend.

A more than 30-degree temperature drop in a matter of days could soon usher in some of the coldest temperatures the Chicago area has seen in years. But when can you expect the dramatic shift?

Monday and Tuesday will see cold temperatures around 18 to 19 degrees during the day, falling to single digits at night.

The drop in temperatures in Chicago has raised concerns about river ice formation, which could lead to ice jams in major waterways.

The dramatic drop in temperatures highlights a continuation of the Midwest's colder-than-usual start to the year. Tuesday's west winds, gusting up to 25 mph, are expected to exacerbate the chill factor,

Temperatures are expected to plunge into the single digits Saturday night and remain there until Wednesday. Wind chill temperatures are expected to reach as low as negative 14 degrees.

After the snow, a cold front will race across the Chicago area Tuesday, sending 'feels-like' temperatures below zero