If you are the kind of angler who tracks snowpack and streamflow reporting, then you know the scoop; it was a big snow year in Montana, with dumps of low elevation snow falling as recently as last week, and we've had plenty of spring rain along with a couple short periods of warmth and sun. What has that all added up to currently? Lots of blue-ribbon rivers in some state of run-off and most are unfishable.
By and large the freestone fisheries across the state are not worth your attention. If you look hard you might find some magic with a clean tributary or a slow, dirty back eddy, but trout-hound favorites like the Yellowstone, Blackfoot, Clark Fork, and Bitterroot are toast for awhile. The Upper Madison, Gallatin, Big Horn (running BIG!), and Paradise Valley Spring Creeks are all fishing fine with some variability and are viable options for you at this time.
Of course our home water the Mighty Missouri River is fishing pretty well even with some increased releases from Holter Dam and spiked flows in the tribs after a major gully-whumper last week. It is a busy river out there so please do you best to share the resource and accommodate all the visiting anglers we'll see for the next month or so.
If you are going to be fishing a tailwater like the Missouri and want to have some productivity then be prepared to fish a deep nymph rig and do it right - safety cast followed by a long drift with lots of easy mending, followed by an assertive hook set with good follow through and a nice re-cast when you realize it wasn't a trout at the other end. Hit it and quit it with all the shotgun casts, halfsie hooksets, limpwristed mends and ill-timed roll casts.
Good luck out there and we'll let you know when the June dryfly game has returned to Montana - it won't be too long now.