Montana ·
Stillwater River Fly Fishing Report - September 20, 2026

STILLWATER RIVER
ReportSEP 20 — 27, 2026
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Flow
512CFS
Stillwater River near Absarokee, MT
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Water Temp
56.1°F
Updated 2026-09-20
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Weather
44–73°F
Chance Rain Showers
💧
Clarity
Clear
Check post-storm
Flow is running at 512 cfs with a gauge height of 1.78 ft — low and clear conditions that demand precise presentations and light tippet. Water temperature is a comfortable 56.1°F, keeping trout active and feeding throughout the day.
What's Working — Hot Flies

Bionic Hopper - Tan #12
#12

Bionic Hopper - Purple #12
#12

Parachute - Blue Wing Olive #22
#22

Top Secret Baetis #16
#16

Juju Baetis Tungsten #22
#22

Egan's Silver Bullet - Baetis #14
#14

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

Egan's Frenchie #12
#12

Olsen's Straggle Stone Brown Barbless #12
#12

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

Black Zebra Midge(TBH) #20
#20

Bionic Ant 2.0 - Black #16
#16
Hatch Chart
| Insect | Size | Activity | Prime Time |
|---|---|---|---|
| Grasshoppers | 12-14 | Moderate | 11 AM - 4 PM |
| Blue-Winged Olive (Baetis) | 20-22 | Heavy | 10 AM - 2 PM |
| Caddis | 18-20 | Moderate | 4 PM - 7 PM |
| Midge | 20-22 | Light | 7 AM - 10 AM |
| Stonefly (late season) | 12 | Light | 9 AM - 12 PM |
Best Time Window
- 8 AM - 11 AM: Foggy, overcast conditions trigger a strong BWO hatch — fish dry flies and emergers in flat tailouts and slow seams.
- 11 AM - 4 PM: Hopper time along grassy cutbanks and willow-lined banks; work the tan and purple Bionic Hoppers tight to structure.
- 5 PM - Dusk: Evening caddis activity picks up in slower pools — switch to the Corn-fed Caddis Tan and dead-drift through foam lines.
Guide's Tip
From the benchWith flows at 512 cfs and crystal-clear water, your approach matters as much as your fly selection — stay low, wade slowly, and cast from downstream. The overcast and fog forecast for the morning will push BWO activity earlier and harder than a bluebird day, so be on the water by 9 AM and work the flat tailouts below riffles with a size 22 Parachute BWO or Top Secret Baetis. Once the sun breaks through midday, shift to the grassy banks with a hopper and work the foam lines tight to the bank with a downstream reach cast. In the evening, switch to a Corn-fed Caddis in the slower pools as caddis begin to skitter.
Main Species
Rainbow Trout
Brown Trout
Yellowstone Cutthroat Trout
