Mid-July usually offers the best fishing of the year in the Lamar system. The only exceptions are when the water is extremely high. So far, we are looking at a near-normal snowpack. Green Drakes, PMD, Yellow Sallies, Little Olive Stones, evening caddis, and streamers all typically work well. Even last year we were fishing the Lamar system by then, and we had a 160% snowpack. In my entire career in Yellowstone (since 2001), I have seen the Lamar system drop into fishable shape after July 10 one time.

Bear in mind that this water can get muddy at the drop of a hat due to t-storms, so be prepared to fish elsewhere if need be. The Gardner and the Yellowstone are great in July.

I'll be putting up our first season forecast in late January, which'll have projected fishable dates based on current snowpack, etc.

Thanks to all for suggesting the OP talk to me.