You probably missed this because you were watching migrating birds or something, but National Grasslands Week was June 18th-24th.
Or maybe you skipped it because the Comanche and Cimarron national grasslands are interesting country but it's just too damn hot there in June for recreation. Especially this year. (There are other national grasslands as well.)
I went to the Purgatory River dinosaur trackway that week in 2015, and while it was a good experience, I would much rather have gone in December. I have hunted in shirtsleeves on New Year's Day in southeastern Colorado.
January is also good, absent any blizzards. Or February. I used to take the nature-writing students out to Vogel Canyon (in the upper-left light-blue area on the map below) in early February.
It's a good entry point for the grasslands experience — all that aridity and melancholy and mysterious rock art.
It must have been someone sitting in an air-conditioned office who put National Grasslands Week in June. The bureaucratic mind at play.