ctbruce,
We stayed at the Wisconsin Dells KOA August 20-21, 2015. The first morning (based on when I took the dog outside) started at 55 degrees and the second morning started at 65 degrees. My journal isn't the best, so I didn't record the high temperatures for the stay. Still, it was a nice visit.
Here's a web page that will give you average temperatures for Wis dells.
http://www.usclimatedata.com/climate...tates/uswi0756
Hope you enjoy your trip!
Craig