September on the Bighorn has a completely different feel than the busy summer months — the crowds are gone, the cottonwoods are beginning to turn gold, and the river is settling into its beautiful fall rhythm. This is one of the most special times of year to be on the water.
Current Conditions — September 2026
Flows are running at 1,310 CFS — clear, wadeable, and concentrating fish beautifully in classic seams, tailouts, and deeper runs. Water clarity is exceptional with 36-48 inches of visibility below the Afterbay. The tailwater below Yellowtail Dam maintains a consistent 45-48°F regardless of air temperature — the reason the Bighorn fishes well year round.
The crowds have thinned significantly. The cottonwoods are just beginning to turn. The big browns are dressing in their vivid fall colors and becoming noticeably more aggressive. This is the Bighorn at its most peaceful and most wild.
The Hatches — September
- Trico — peak spinner falls at first light. August through September is prime. Position yourself in the flat water below the riffles at sunrise and watch for subtle sipping rises.
- Blue Winged Olive (BWO) — building on overcast afternoons. Fall is arriving and the BWO hatch is strengthening. Watch the softer water carefully on cloudy days.
- Midge — reliable all day, especially mornings. Never leave the boat without midges.
- Caddis — evenings along the banks, tapering off from the August peak.
- PMD — still showing on overcast mornings, winding down for the season.
What's Working Right Now
Nymphs
- Tailwater Sowbug #16 — always in the rig, never wrong
- Trico Spinner Nymph #20-22 — dawn and early morning
- TH Zebra Midge, Black #18-20 — essential morning pattern
- Juju Baetis Tungsten #22 — BWO nymphing on overcast afternoons
- Egan's Frenchie #12 — excellent in the seams
- RS2 Grey/Olive #18-20 — reliable and proven
- Ray Charles Grey #14-16 — legendary Bighorn pattern
- Pinky Pink #16-18 — consistently producing
Dries
- Trico Spinner Black/White #20-22 — first light on calm mornings
- CDC Baetis #18 — BWO hatch on overcast afternoons
- Parachute BWO #22 — fall BWO activity building
- Elk Hair Caddis Black #16 — evenings along the banks
Streamers
- Coffey's Sparkle Minnow Sculpin Olive #6 — first and last light
- Olive Woolly Bugger #6 — along undercut banks
- Black Leech #10 — deeper runs as browns begin staging for fall
Best Access Points
- Afterbay — upper river, crystal clear water, excellent dry fly and nymphing water
- 3 Mile — most popular access, excellent for both wade and float fishing
- Bighorn FAS — lower river, good for streamer fishing as browns stage for fall
Best Stretches
- Afterbay to 3 Mile — upper river, crystal clear, prime dry fly and nymphing
- 3 Mile to Bighorn — excellent streamer water as browns begin staging
Tips for September
Start each morning with the Trico spinner fall — position yourself in the flat water at first light and drop down to 5X or 6X tippet with an extra 12 inches of leader to eliminate micro-drag in September's clear low water.
On overcast afternoons watch carefully for BWO activity in the softer water — this hatch is building as fall arrives and will be the most reliable dry fly opportunity through October.
As the month progresses add streamer fishing to your rotation. The big browns are staging for the fall spawn and are becoming increasingly aggressive along undercut banks and in the deeper runs. Once you find a pod of feeding fish stay put — they are grouped and consistent right now.
Note: Aquatic vegetation is present below 3 Mile. Target clean lanes between weed beds for the best results.
A Note on Licenses
Montana Fish, Wildlife & Parks no longer allows fishing licenses to be sold at the lodge or any fly shop. Purchase your license online at ols.fwp.mt.gov before you leave home. Cell service can be unreliable in Fort Smith — take care of this before you arrive.
Call us at 800.665.3799 or email info@forrestersbighorn.com.
Forrester's Bighorn River Resort — Fort Smith, Montana
Orvis-endorsed fly fishing since 1992 | 800.665.3799 | forrestersbighorn.com