Montana ·
Bighorn River Fly Fishing Report - August 23, 2026

BIGHORN RIVER
ReportAUG 23 — 30, 2026
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Flow
1250CFS
Bighorn R bl Yellowtail Afterbay Dam nr St. Xavier
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Water Temp
—
Updated 2026-08-22
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Weather
61–94°F
Chance Rain Showers
💧
Clarity
Clear
Check post-storm
Flow is running 1,250 cfs out of Yellowtail Afterbay Dam with crystal-clear tailwater conditions — ideal for both nymphing and surface presentations. Gauge height is sitting at 59.41 ft, a comfortable mid-summer level that puts fish in predictable feeding lanes across riffles and seams.
What's Working — Hot Flies

Bionic Hopper - Tan #12
#12

Bionic Hopper - Purple #12
#12

Bionic Ant 2.0 - Black #16
#16

Corn-fed Caddis (CDC) Tan #20
#20

Corn-fed Caddis (CDC) Olive #20
#20

Tungsten Split Case Nymph - PMD #20
#20

Egan's Thread Frenchie Jig - Olive #12
#12

Tailwater Sowbug - Rainbow #10
#10

Tungsten Tailwater Sowbug - Rainbow #10
#10

Egan's Frenchie #12
#12

Parachute - Blue Wing Olive #22
#22

Coffey's CH Sparkle Minnow Sculpin #6
#6
Hatch Chart
| Insect | Size | Activity | Prime Time |
|---|---|---|---|
| Black Caddis | 16-18 | Heavy | 6 PM - 8 PM |
| Tan Caddis | 18-20 | Moderate | 5 PM - 7 PM |
| PMD (Pale Morning Dun) | 18-20 | Moderate | 9 AM - 12 PM |
| Trico | 22-24 | Light | 7 AM - 9 AM |
| Terrestrials (Ants & Hoppers) | 12-16 | Heavy | 11 AM - 4 PM |
| Midge | 20-24 | Light | 7 AM - 9 AM |
Best Time Window
- 6:30 AM - 9:30 AM: Early Trico and midge activity in flat water; nymph sowbugs and Frenchies through riffle heads before boat traffic picks up.
- 9:30 AM - 12:00 PM: PMD window peaks — nymph the split-case PMD through riffle runs and watch for risers in slower flats.
- 5:00 PM - 8:00 PM: Prime evening caddis hatch; fish CDC caddis patterns in the film along foam lines as black and tan caddis fill the air.
Guide's Tip
From the benchWith flows at 1,250 cfs and gin-clear water, fish are spooky — go long with a 12-14 foot leader and size down your tippet to 5X or 6X for nymphing. During the heat of the day (11 AM to 3 PM), walk the grassy banks and target rising fish with terrestrials, presenting from a downstream position to avoid lining them. Watch the sky closely between noon and 3 PM: the slight storm chance could trigger a brief BWO or caddis flurry that puts fish into a feeding frenzy — have a dry fly rigged and ready to switch instantly. Post-storm, the water may carry a slight color bump near tributary mouths, so shift to a Sparkle Minnow or streamer and work the edges hard.
Main Species
Brown Trout
Rainbow Trout
Mountain Whitefish
