What About Arkansas?

The closest place to DFW that I might suggest in Arkansas is Queen Wilhelmina State park which sits at about 2,600 ft elevation on a mountain near the Oklahoma / Arkansas line. There is not a lot to do there, it is a small state park with a few nature trails and a miniature train that runs around the perimeter of the campground a few days per week, located along a scenic ridge line drive outside Mena Arkansas. I spent a couple of nights there on the way home to Louisiana after the big solar eclipse last summer waiting for Hurricane Harvey to get out of the way. The weather was nice when I was there, though there was pea soup thick fog in the mornings, of course as you likely know hurricanes mess with the usual weather patterns. I have read that the highway that passes right by the length of the campground is popular with motorcycle riders, though did not experience this when I was there. Beyond that there are a number of deep lakes in Arkansas with nearby campgrounds that may be a little cooler than you will find in the DFW area.

See http://www.queenwilhelmina.com/park-information/current-weather.aspx