I live in the Midwest and understand this concern. We aren’t fans of the heat and subsequently do our river paddling in the shoulder seasons. The “cold” does a solid job of eliminating the riff raff.
We do like to beat the heat by sea kayaking on the Great Lakes at the height of summer. Unfortunately, we’ve had a couple of run ins. We tend to go far out into the lake and, once out there, there is so much space that we really don’t encounter people. Where we have issues are near the launches. I hate to stereotype, but our issues have been with jet skiers who don’t seem to have an understanding of the rules of the water. They often get too close. We will remind them. On one occasion a jet skier got belligerent with my wife. The belligerent jet skier was shocked at the speed at which I could cover some water in my sea kayaking as I followed him to the ramp. He could not apologize loudly or often enough as I hopped out of my kayak and ran to his trailer with smoke coming out my nostrils brandishing my paddle.
These people scare me- and they have a tendency to turn me into a person I’m not often proud of.