With low temperatures, snow will "readily accumulate" on roads, and an inch or more is possible in some areas.
Cold conditions will continue into Wednesday morning, with wind chills potentially as low as minus 35 below zero.
Highs will only be in the single digits on Sunday, Monday and Tuesday.
Friday will be the warmest day of the week, with a high of 43.
Arctic cold is also on the way for northern Illinois.
Throughout January, Venus, Saturn, Jupiter and Mars will align in the night sky, according to NASA.
Below normal temperatures will continue this week and into the weekend for the Chicago area.
The highest snow amounts are expected across Lake County and central/northern Cook County on Monday.
A winter storm could impact travel from Sunday into Monday; here's what we know so far.
Wind chills could get as low as -10 degrees this weekend, according to the National Weather Service.
The rainy start to New Year's Eve could transform into flurries as the new year approaches.
The Climate Prediction Center has released its 8-14 day temperature and precipitation outlooks which gives us a look at early January.
Fog is also expected through Thursday morning, with some areas of locally dense fog.
Temperatures will have highs in the 40s all week, and will even peak in the 50s on Friday.
Snow showers will continue Friday morning, with a high of 35 degrees. By Monday, the high is 45.
The winter solstice on Saturday will be the shortest day of the year, with only 9 hours and 7 minutes of daylight in Illinois.
The weather service said that a period of snow is expected late Thursday afternoon into the evening, especially north of I-80.
We have had a white Christmas 56 times since 1884, according to the report earlier this month from The Weather Channel.
Snow could impact the Wednesday morning commute, especially for areas north of Interstate 80.
A dense fog advisory is also in effect Monday morning for the Chicago area.
Earlier in the day on Saturday will be dry, but rain is expected late Saturday into Sunday.
With Christmas Day now in the long-range weather outlook, does a white Christmas look likely?
Snow showers are also expected as the cold front moves into the area Wednesday.
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"Temperatures will tumble" on Wednesday, bring a sharp cold blast of air.
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The next chance of precipitation is Sunday night, especially for areas southeast of I-55, the weather service said.
Gusts of 45 mph are possible with wind chills of 15 below zero possible early Thursday.
See predictions from NOAA, AccuWeather, The Old Farmer’s Almanac and The Farmers' Almanac for winter in Illinois.
Below zero wind chills are expected Thursday morning.
Single-digit wind chills are possible Saturday and Sunday mornings, the weather service said.
Temperatures on Thanksgiving night will drop into the teens.
There's a 30 to 40 percent chance of wintry weather for Tuesday through Thursday.
Will weather impact your travel plans for Thanksgiving Day? Here's the outlook in Illinois.
Snowfall rates could approach an inch per hour for a few hours on Thursday morning.
Rates up to 1 inch of snow per hour are possible on Thursday morning.
"We may see rain mix with or change to snow Wednesday night into Thursday morning, the first of the season," the weather service said.
"Mild temperatures will persist into early next week amid plenty of cloud cover," the weather service said on its Facebook.
Monday will be windy with gusts as high as 25 mph, and temperatures will fall after a cold front in the afternoon, the weather service said.
"Tranquil conditions" are expected on Friday and Saturday, before rain in the evening.