Hello. I'm a little familiar with the Chicago climate here
. Air conditioning in the summer is a must. With a/c the summer humidity can hang around 70%. While on the high side, when kept on a dry substrate like aspen, it's fine. If you are heating with ceramic emitters or heat panels they are even more drying so you should be fine.
I have glass vivs with UTH and my snakes are fine in the summer. In fact, I still provide humid hides with sphagnum year round and let the snakes decide. In the winter, with forced air heating, the humidity can get too low, like down to 25 %. I find partially covering the screening with plastic wrap keeps things at a very safe 50%.
Of course, your set up will be quite different from mine. The point is that I consider a/c absolutely essential, and a defumidifier is not needed my experience.
Best wishes!
P.S. The recommended humidity for corn snakes is 40 to 60%