As with August, most of September is a tough month for fishing on the Boulder River near Big Timber, Montana. Low water, coupled with warm air temperature creates a stressful environment for the trout. Cool-weather and shorter nights quickly bring a reprieve to the Boulder River trout by mid-September as fall arrives.
Irrigation demands continue to keep flows very low, historically, through late September.
As the water cools down and recreational traffic diminishes, the adventurous angler can find solitude and rewarding days along the upper river and near the Boulder Forks FAS.
Terrestrial insects such as grasshoppers, ants, and beetles continue to be the foundation for the Boulder River trout diet in September.
The arrival of cool air and cloudy weather reignites BWO mayfly hatches and Western Red Quill hatches are common on rainy days along the lower river
Beetle patterns become most effective in mid-September, fish these on long leaders to help perfect a drag-free drift along the seams next to mid-river boulders. We prefer to fish a small, single dry like the Hi-Viz Foam Beetle on 5x tippet when we can spot feeding trout sitting in the eddies behind a rock or boulder.
Low, clear water calls for stealthy approaches and accurate fly presentations for anglers fishing the Boulder River in early fall. Overcast conditions can bring trout to the surface during hatch periods. Dry fly fishing is the mainstay for fly fishing to these wary trout during this time of the year.
However, nymph fishing with 9’ leaders and 5X tippet becomes productive in the deeper pools and runs near Big Timber and 8-Mile bridge as hatch activity resumes in September.
Our Bozeman fly fishing guides use tandem nymph rigs with two, small flies in these low water conditions. Attach a strike indicator about 4’ above the first fly and add weight as needed. We prefer sparse patterns in dark colors to imitate the most active aquatic insects like Midges and BWO nymphs.
Boulder River levels are historically, very low through September until local irrigators reduce their demands once fall settles into the region. Cooling temperatures and shortening days quickly reinvigorate the trout in the river. However, the low flows make for challenging angling conditions, and floating in rafts is nearly impossible.
Overcast conditions and cooing water bring blanket hatches of BWO and Pseudocleon mayflies. Brown Trout start to migrate throughout the river drainages, becoming increasingly aggressive as their fall spawning season approaches. There are many great Montana fly fishing options near Bozeman in September, but anglers focus their efforts on the larger mainstem rivers for the best success.
Fins and Feathers Guide Service has been outfitting Montana fly fishing day trips near Bozeman – and across the Treasure State – for over 23 years. Our talented team of patient, expert Montana fly fishing guides welcomes anglers with all skill levels and tailors each day to your interests. Reservations can be secured online, via e-mail, or over the phone by calling us at 1-406-468-5019.