I spent Friday evening fishing on the Blackfoot River and had a decent afternoon...nothing great but I ended up catching 10 fish. One was 15" and another 18" but the others were all 10" or smaller. All fish were cutthroats. The hot weather has heated the water up so fishing in the mornings and later mornings would probably be more productive. As often happens on the Blackfoot, I caught a fish on the very first catch which is just one reason why the Blackfoot is an Idaho fly fishing treasure. If you go, try the Stocking Ranch or the 8 mile stretch in the Monsanto property (you'll have to walk a lot!) for excellent fly fishing.
Hot flies: Size 10 and 14 gray-colored foam hoppers. My dad also caught some on size 16 bead headed prince nymphs