Montana ·
Bighorn River Fly Fishing Report - May 31, 2026
BIGHORN RIVER
ReportMAY 31 — JUN 7, 2026
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Flow
1500CFS
Bighorn R bl Yellowtail Afterbay Dam nr St. Xavier
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Water Temp
—
Updated 2026-05-30
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Weather
47–71°F
Showers And Thunderstorms Likely
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Clarity
Clear
Check post-storm
The Bighorn is running a steady 1,500 cfs below Yellowtail Afterbay Dam with excellent clarity and stable tailwater conditions — ideal for both wade and float anglers. Stormy weather overnight through Sunday (60% precip, WNW winds 21–26 mph) will suppress dry-fly activity, but Monday's clearing skies and 71°F high set up the best window of the weekend.
What's Working — Hot Flies
Tungsten Tailwater Sowbug - Rainbow #10
#10
Blowtorch - Hare's Ear #12
#12
Egan's Thread Frenchie Jig - Olive #12
#12
Pheasant Tail Tungsten #20
#20
Egan's Silver Bullet - Baetis #14
#14
Top Secret Baetis #16
#16
Black Zebra Midge (TBH) #20
#20
Roza's Pink Pheasant Tail - Barbless #16
#16
Stealth Link Mercer - PMD #20
#20
Parachute - Blue Wing Olive #22
#22
Egan's CDC Rainbow Warrior #22
#22
Corn-fed Caddis (CDC) Tan #20
#20
Hatch Chart
| Insect | Size | Activity | Prime Time |
|---|---|---|---|
| Blue-Winged Olive (Baetis) | #18–22 | Strong | 10 AM – 3 PM, especially on overcast days |
| Midges (Chironomidae) | #20–24 | Strong | Morning through midday; pupae active all day |
| Sowbugs / Scuds | #14–18 | Strong | All day sub-surface |
| Caddis (early season) | #16–20 | Emerging | Afternoon; first hatches of the year building |
| Pale Morning Dun (PMD) | #16–20 | Spotty | Midday; beginning to show on warmer afternoons |
Best Time Window
- Sunday 10:00 AM – 1:00 PM: Brief midday lull between storm bands may trigger a BWO hatch in slower water; nymph the protected inside seams with heavy rigs
- Sunday Night after midnight: Winds drop to 7–21 mph and precip clears — a good time to rest and prepare for Monday's prime window
- Monday 9:30 AM – 2:30 PM: Best window of the period — mostly sunny, 71°F, light south wind; expect strong BWO activity 10 AM–2 PM and early PMD emergence by midday in riffles
Guide's Tip
From the benchWith stormy weather and strong WNW winds through Sunday, focus your effort on the protected inside bends and soft-water edges where fish stack out of the current — heavy nymph rigs with a sowbug lead and a small Baetis or midge dropper will be your most consistent producers. Run a 9-foot leader from indicator to split shot, then 16–18 inches of 5X fluorocarbon to your lead fly and another 16–18 inches to your trailer. Monday is your prime window: clearing skies, 71°F, and a light south wind will fire the BWO and early PMD hatches — be on the water by 9:30 AM and watch the slower flats and back eddies for rising fish by late morning. When you spot risers, switch to a Parachute BWO or CDC Rainbow Warrior and present upstream with a long, drag-free drift.
Main Species
Brown Trout
Rainbow Trout
Mountain Whitefish
