Many avid anglers target September as their preferred month for fly fishing in Montana. Once kids go back to school the amount of tourist traffic visiting the Big Sky state drops off dramatically so the casual anglers sneaking in a guided day of fishing on their Yellowstone Park vacation almost vanishes and the rivers are left to more serious fly fishers. Locals also begin turning their attention to the fall hunting season so the trout see relatively few flies in the autumn months. September also offers some of the most pleasant conditions of the year with relatively dry weather, crisp mornings, and warm days. Fortunately the fishing can be very good in September with a mixed bag of dry fly fishing, streamer fishing and nymph fishing.
Where to fish? All of the favorite classics that fish well in the summer are still a good option in September. Legendary rivers like the Upper Madison, Yellowstone, Gallatin etc still produce good fishing. One of the perks about fishing in September is that several of the lower elevation rivers also become a good option. Waters such as the Lower Madison, Upper Missouri, Jefferson and Lower Gallatin often get too warm in the popular mid summer months to produce good fishing. Once the nights become longer and temperatures begin to drop a bit these fisheries often hit ideal trout temperatures and once again become productive. The lower elevation waters often have lower trout counts per mile but often produce some of the larger brown trout in the region with a ten-pounder a possibility for a very lucky angler. Spring creeks are also an interesting choice for September. By the end of the month the fall baetis hatch is producing steadily mid day with match the hatch fishing. Earlier in the month terrestrials are the main dry fly staple, but nymphing the troughs with midge larva will produce when fish aren't eating on the surface. Usually the famous spring creeks near Livingston only book a few rods a day in September so you can have all of the best runs available without a lot of other anglers around (just be prepared for technical fishing).
Dry fly fishing September offers ample opportunities for anglers that enjoy surface action. In the beginning of the month the terrestrial fishing with ants, hoppers and beetles is often the most productive. Although everyone starts to get really excited about hopper fishing as early as late July, some years the hopper fishing doesn't hit its prime until September. Terrestrial fishing is generally good the entire month, especially on the warmer sunny days which make up the bulk of the days during this dry and mild time of the year. By the middle of September we begin to see some of the mayfly hatches in the region that can get the trout very excited. Tricos are still on some of the waters in early September but by mid September we begin to see baetis mayflies, mahogoany duns, and grey drakes. Even sparse hatches in September can provide some nice dry fly opportunities.
September streamer fishing Brown trout are just beginning to get colored up but are not really on the move yet prior to spawning and will get more aggressive moving into October. Streamer fishing can still be a good option in September. Since the mornings are arriving later with the longer days it is easier to get to the rivers at first light which is often the window to get nice streamer action on sunny days. Of course if you have cloud cover or a front pushing in streamers can be effective throughout the day. Generally September sees a few cold fronts that come in and produce a bit of precipitation for a day or two which can really turn some big fish when fishing streamers.
Nymph fishing It's no secret that trout take the majority of their food subsurface so nymph fishing will always produce regardless of the season. In September we often try to find dry fly opportunities but we still do a lot of nymph fishing. On some of the lower elevation rivers mentioned earlier there are some really big trout and even if a few trout are rising we often still nymph big sculpin and crayfish patterns with a smaller baetis nymph dropper to try to entice some of the trophy trout in these waters. September is certainly high on the list as a great time to visit Montana. If you are looking for a time of year that produces dry and mild weather with fewer anglers on the water then it should be high on the list. The diversity of opportunities that can be experienced in the early fall is also a bonus to traveling during September.