June is good month we think to venture thru the upper midwest (MN, WI, MI) The parks are open by then and the weather hasn't gotten so humid yet. And of course the bugs aren't bad by then either. If you head north to along the shores of Lake Superior (a drive well worth the time) the temps and weather conditions can change daily, so prepare of hot, and wet & cold. MI has some wonderfull national parks (most rustic, but not at all crowded) campgrounds. The UP is GREAT! Be sure the check out the sand dunes and MN's North shore is wonderful. too. Have a great trip!