We were there last June the weekend following the cool weather and it was 102. We cut our stay short and headed further North. Great area tho!
Also a big change was the bugs came out in force the hot weekend. We had friends that were there the weekend before and there wasn't any bugs. Take a good High count Deet bug spray with you. As posted earlier, it can be freezing or frying!
June is right in the verge - it can be cool or hot. We spent about a week in that area last June, and some days got hot - high 90's, but others stayed cooler. We were there in the middle of the month, and it does get hotter as you get closer to July.
It's a bit of a gamble (weather-wise), but we took that bet because it's such a beautiful area.
2003 Country Coach Intrigue, Cummins ISL 400
Toad: 2006 Jeep Wrangler Unlimited (LJ) toad, with just a few mods...
Other rig: 2005 Chevy Silverado 3500 Duramax Dually / Next Level 38CK Fifth-wheel Toy Hauler w/ quads, sand rail, etc...