Chisos Mountains in Big Bend
There are a decent enough sites that you should be able to find one with shade if you get there early, but some of them are exposed. The restrooms have heaters for the winters and are kept clean. There are no showers up here, but the lodge is close by if you are in dire straights for some wifi. There is almost never an issue with getting a site in Big Bend, but it never hurts to get there early to ensure a good a site!