Free Resource · Updated 2026
The Bighorn River below Yellowtail Dam in Big Horn County is one of the finest tailwaters in the Rocky Mountain region. Cold clear releases produce exceptional populations of large brown and rainbow trout with excellent hatches year-round.
Bighorn River Hatch Calendar — Quick Reference
The Bighorn tailwater stretches roughly 13 miles below Yellowtail Dam near Fort Smith, Montana. The Wyoming portion of the fishery is less well-known than the Montana section but holds the same quality of fish. Consistent tailwater temperatures mean midges and BWOs fish well even in January.
PMD hatches in July produce excellent surface action and trico spinner falls in August can create dense feeding lanes of rising fish. Hopper fishing is also productive in August on the banks. The mahogany dun hatch in September extends quality dry fly fishing well into fall.
The lower Bighorn in Wyoming is accessed via Wyoming Game and Fish access points. Float fishing is the most efficient way to cover water on this wide, powerful river. Local guides provide drift boat trips that make the most of the extensive fishable water.
See the full Wyoming Fly Hatch Chart for hatch timing across all of Wyoming's top trout streams.
Check Conditions Near Bighorn RiverWhat to Fish
Baetis spp.
BWOs are the most important year-round hatch on the Bighorn tailwater. They come off during overcast conditions throughout the year and trigger heavy feeding. April and October are the best months.
Recommended: BWO Parachute #18-22
Ephemerella infrequens
PMD hatches in July are one of the highlights of the Bighorn dry fly season. The dense fish populations mean many rising fish are visible during a good afternoon hatch.
Recommended: PMD Parachute #16-18
Tricorythodes spp.
Morning trico spinner falls on the Bighorn draw fish into feeding lanes in late summer. The flat, slower sections concentrate both the spinners and the feeding fish.
Recommended: Trico Spinner #20-22
Chironomidae
Midges sustain winter fishing on the Bighorn tailwater. Two-fly midge rigs fished through deep pools on cold clear days can produce surprisingly large browns and rainbows.
Recommended: Mercury Midge #20-24
Common Questions
The Bighorn River enters Wyoming from Montana and flows through Big Horn County. The tailwater fishery is accessed from Fort Smith, Montana, and extends downstream into Wyoming.
The Wyoming portion of the Bighorn tailwater holds the same quality of fish as the Montana section. It typically receives less pressure and provides good access through Wyoming Game and Fish areas.
Yes. Cold tailwater releases from Yellowtail Dam maintain consistent water temperatures throughout the year. Midges and BWOs fish well even in winter.
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