Not all of it, but parts of the Midwest especially. I'm too lazy to find the numbers right now, but the basic way to measure how much "extreme" (of a certain type) weather you have is to add up heating degree days plus cooling degree days. 65 is the base, so a day which is 90 is a 25 degree cooling degree day, and a day which is 40 is a 25 degree heating degree day. 65 degrees every day would add up to zero over the year. Lots of high temp days and low temp days give you a big number.
There are hotter places and there are cooler places, but Chicago is really fucking hot and really fucking cold. Mid-Atlantic not much better.
