Bighorn River Fly Fishing Report - September 27, 2026

Fly Fishing Report

BIGHORN RIVER

Report
SEP 27 — OCT 4, 2026
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Flow
1490CFS
Bighorn R bl Yellowtail Afterbay Dam nr St. Xavier
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Water Temp
—
Updated 2026-09-26
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Weather
45–66°F
Mostly Cloudy
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Clarity
Clear
Check post-storm
Flow has dropped to 1,490 CFS (gauge height 60.47 ft) — down from 1,680 CFS last week and trending toward ideal nymphing and dry-fly conditions with excellent clarity. Overcast skies today with a high of 66°F set up a long, productive hatch window for fall baetis and midges.
Hatch Chart
Insect Size Activity Prime Time
Blue-Winged Olive (Baetis) #20-22 Heavy 10 AM - 3 PM
Midge #20-24 Moderate 8 AM - 11 AM
Caddis #18-20 Light 4 PM - 6 PM
PMD (Pale Morning Dun) #18-20 Light 11 AM - 1 PM
Sculpin / Streamer Forage #4-6 Moderate 7 AM - 9 AM
Best Time Window
  • 7 AM - 9:30 AM: Low-light streamer and midge fishing; target deep outside bends and slower inside eddies before the sun angle rises.
  • 10 AM - 2 PM: Prime BWO hatch window under overcast skies; switch to dry flies or CDC emergers in flat seams and tailouts.
  • 4 PM - 6 PM: Late-afternoon caddis trickle and nymph feeding; work the riffles and gravel runs with small olive nymphs before dark.
Guide's Tip
From the benchWith flows at 1,490 CFS and dropping, the Bighorn is fishing as clean as it gets this time of year — wade the inside seams of the main channel and focus your nymphing rig in the 2-4 ft depth range where rainbows and browns are stacked. The overcast sky today is your best friend for the BWO hatch; expect fish to commit to dry flies from 10 AM through early afternoon, so have a size 22 Parachute BWO rigged and ready before you leave the truck. For big browns, hit the deeper outside bends with a streamer in the first 90 minutes of light — they're actively feeding ahead of the fall spawn. When the hatch dies down, drop back to a tight-line nymph setup with a heavy anchor fly and a small Perdigon or Blowtorch trailing 12 inches behind it.
Main Species
Brown Trout
Rainbow Trout
Mountain Whitefish
Report generated September 27, 2026 — Next update: October 4, 2026