Stillwater River Fly Fishing Report - September 20, 2026

Fly Fishing Report

STILLWATER RIVER

Report
SEP 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.
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
Report generated September 20, 2026 — Next update: September 27, 2026