This is gonna sound dumb to a lot of you but Rock Island Wisconsin. It's a small island in lake Michigan that was originally a rich inventor's vacation retreat and has since been made into a state park. The summers are hot but the lake is nice for swimming in. There's some beautiful scenery, good fishing, it's close enough to civilization that you can go shopping or catch a movie with only a few hours travel. The winters aren't too severe. I would quite happily live in a tent there for the rest of my life if I could.