a few years ago, after attending the Sturgis rally, I continued on to Yellowstone. Great time. I stayed in Cody, Wy, then the next morning I rode into Yellowstone. I had so much fun looking around, that I lost track of time. About 5pm,I started to think, where am I going to camp tonight? There were 2 campsites at Yellowstone, and luckily, they had a spot for a motorcycle. I had no tent or sleeping bag. You know, this is August, and Sturgis was in the 90's. Well, the campground was around 7500 ft elevation, so guess what, it got real cold overnight. Frost on the ground. I did have a small tarp, tied onto the side of the bike, which I crawled under. I had every piece of clothing I brought, on me. About 5;30 am, I had to get up and take a fast walk, to get my blood moving. I had no food with me, as I was eating at resturants on my trip. So, your pulling a camper, should resolve most of the stupidity that I had, but with a camper, yes, make rsvp in advance, if your planning to stay in Yellowstone, and bring some food. Just don't leave any food outside at night, or you may find a bear in your campsite. I would not recommend trying to stay there, around the Sturgis rally. People like me, flood the place. June- may have some snow, but shouldn't be too much. Enjoy!