For those looking for a place to cool off in August, let me suggest Turquoise Lake, CO. Turquoise Lake is located near Leadville, which is the highest incorporated city and the second highest incorporated municipality in the United States. At 10,152′, expect cool nights in the low 30′s, even in the middle of the summer.
Camping at Turquoise Lake consists of 8 Forest Service campgrounds with 300 campsites spread around the lake (Map) and two boat ramps available, one on each side of the lake. While there are no hookups at any of the campgrounds, flush toilets and fresh water are available at each & there is a dump station at the Molly Brown campground. The clear nights provide an excellent view of the stars over the lake.
Reservations for the Forest Service campgrounds are available through Reserve America. Here is a link to the Molly Brown Campground. Do a search for Leadville campgrounds for the others. While I had no problem finding a site during the week, all sites were booked for the weekends during August.
These are popular campgrounds during the summer, particularly during August when Leadville has a number of interesting events.
In addition to the scheduled activities, Leadville has many roads and jeep trails that provide visits to the abandoned mines in the area. You can even take County road 4 over Hagerman Pass to CO 82 and Glenwood Springs to visit Hanging Lake, one of my earlier posts.