Firehole River has warmed to the point that trout within are in danger of exhaustion when being played. That is because geothermal water now makes up a higher component in its flow. Iron Spring Creek and the Little Firehole River have cooler water, so trout from the river seek refuge in these during summer. When cooling atmosphere arrives in September the Firehole River will again be in better thermal shape for trout.
Shoshone and Lewis Lakes are warming meaning fish are heading to deeper water. Go to a full-sink line and get out in the lakes for best chance of success.
Lamar River drainage streams are now in good shape for fishing. Being close to roads, especially lower Slough Creek, Soda Butte Creek, and Lamar River in it meadows, expect crowds of anglers to develop. Avoid the most of these by fishing early (spinner falls) and late (PMDs, caddis, ants & beetles, a few golden stones).
Fall River Basin streams are low and clear, meaning they will be tough fishing during these bright, clear days. Expect best dry fly fishing to take place during a cumulus build-up with increase in relative humidity (the drier the atmosphere, the lesser the aquatic insect emergence), all leading to a thunder shower threat. Hey; this train of thought applies to any of our streams!