The desert rivers of the Southwest are at their nicest in the fall. Unlike the spring, flows are mellow, and between the summer and winter the brutal Utah temperature gradient evens out. The days stop being scorchingly hot, and the nights aren’t freezing. Desolation and Grey canyons, which sit back-to-back on the Green River and contain 86 miles of Class II-III whitewater, are perfect for beginner kayakers or rafters who want a little more than a float trip. The Bureau of Land Management administers permits through a lottery and keeps group sizes small, so the river is nearly unpopulated. John Wesley Powell and his crew named the first canyon Desolation because they ran it after nearly dying in Lodore Canyon, directly upstream. Aside from the whitewater, Deso and Grey have endless opportunities for side hikes and canyon exploration, as well as a lot of good, unvandalized petroglyphs.