Below 20...not 20 below zero.
View attachment 1579870
???
I said 20 and I also said 20 OR below.
And this is just an example of one week. Where I am located, it tends to be colder then in Chicago. The point is that it is cold and it can be dangerous, it would be rare not to see consecutive days in the negatives.
Last year it would be in the negatives and then go up to the 50s. Absolutely crazy weather. There really is no way to prepare for it, so it's best to assume the worse case scenario.