The upper Teton has been fishing well with PMDs, Yellow Sallys and caddisflies. You should go early, not only because of the heat but also because the river gets covered up with recreational floaters. They are always on the river this time of year but the hot weather really brings them out in droves. Amazingly, the trout continue to feed right through the madness so if you can tolerate the noise and people you can do pretty well, especially during the morning and evening hours. The Teton Canyon is fishing very well. It always pays dividends to get out early, try and fish this stretch before the heat of the day sets in.