The advisory will from 11 p.m. Saturday to noon Sunday. Wind chills of 20-25 degrees below zero are expected.
Chicago Weather: 7-Day Forecast
A wind chill warning is in effect for far west and northwest suburbs.
Snow spread into the region starting late Friday night and continues into early Saturday, with on and off snow showers expected throughout the day Saturday, according to ABC7 Meteorologist Cheryl Scott.
About 1 to 3 inches of light snow accumulation is expected in total Saturday, with higher amounts near Lake Michigan in Northwest Indiana. Slick roads and reduced visibility are expected, so drivers should take extra care when traveling.
The snow will be followed by plummeting temperatures Sunday, leading perhaps to the coldest Valentine's Day on record.
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Wind chills of up to -30 are expected on Sunday.
The deep freeze may not be the coldest in Chicago history, but the length of the cold snap has been notable, weather service meteorologist Ricky Castro said. Chicago dipped below 25 degrees on Feb. 5 and hasn't gone above that temperature since.
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Lake Michigan along the city's shoreline looks like a glacier, with more than 90% of it covered in ice. The sight has attracted small, bundled crowds willing to brave bitter temperatures for a glimpse at our urban tundra.
But the cold causes all kinds of problems. A pipe broke at the former Apple store on Michigan Avenue, sending water everywhere and creating a slippery, slushy mess on the street. The dangerous cold on the way poses a direct hazard for anyone outside and drivers on the roads.
Cars themselves also struggle with temperatures like this, especially when buried in snow for days on end.
"Batteries are going off the shelf, tires are blowing out, any fluid that was questionable is starting to freeze,' said Matt Tefka, owner of Fulton Desplaines Garage. "The absolute worst thing you can do to a car in general is let it sit, let alone letting it sit in literally ice and making it become a moving igloo."
The city also said it's working around the clock to try to make sure the most vulnerable citizens are warm and protected.
Considering a forecast that has the city staying below 25 degrees into next Friday, the cold snap will be entering record-setting territory with possibly 15-straight days spent in extreme cold.
A two-week stretch of 25-degree or lower days would place it in the top 10 longest periods ever in Chicago, Castro said. The current record stretch of sub-25-degree days was set in 1899 with a period of 19 days.
While the city might not break that record, there are easier targets. Chicago had a two-week stretch of sub-25-degree days in 2018, and again in 2017. In 1984, the city went through 17-straight days of temperatures below 25 degrees.
Safety essentials for ice storms
The city of Chicago urging everyone to prepare for this weekend's extreme cold. That includes wearing several layers of loose, warm clothing and keeping your head, hands and feet covered outdoors.
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To keep your pipes from freezing, the city recommends letting water drip from your faucets.
If you're driving, have a full tank of gas, flashlights, blankets, snacks and water in your car in case of emergency,
For people without heat, or who don't have adequate shelter from the cold, the city will have two overnight warming centers: One at the Garfield Community Service Center on South Kedzie Avenue and the other at the Dr. Martin Luther King Community Service Center on South Cottage Grove Avenue.
Both will be open from 9 a.m. until 5 p.m. Monday.
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In addition, the city has dozens of other locations where people can seek shelter during the day, including at the Chicago Cultural Center, public libraries, Park District locations and local police departments.
To locate a center nearby, residents can call city services at 311 or visit 311.chicago.gov.
The city also asking people to shovel and salt in front of their homes and businesses and to check on neighbors.
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Fire officials also remind people to make sure their smoke detectors are working - citing a recent rash of fatal fires and offering a reminder not to use stoves for heat and to keep space heaters at least three feet away from anything combustible.
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Sun-Times Media contributed to this report.