Wyoming ·
Firehole River Fly Fishing Report - September 6, 2026
FIREHOLE RIVER
ReportSEP 6 — 13, 2026
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Flow
190CFS
Firehole River near West Yellowstone MT
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Water Temp
70°F
Updated 2026-09-06
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Weather
39–72°F
Mostly Clear
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Clarity
Clear
Check post-storm
Water is running at 70°F and 190 cfs — right at the upper edge of the comfortable window, so fish early before afternoon thermals push temps higher. Clarity is good heading into today's sunny weather, but tonight's storm system could bump turbidity by Monday morning.
What's Working — Hot Flies
Parachute - Blue Wing Olive #22
#22
Juju Baetis Tungsten #22
#22
Black Zebra Midge(TBH) #20
#20
Olsen's Peacock Blowtorch Barbless #22 - 24
#22-24
Bionic Ant 2.0 - Black #16
#16
Bionic Ant 2.0 - Brown #12
#12
Corn-fed Caddis (CDC) Tan #20
#20
Pheasant Tail Tungsten #20
#20
Egan's Silver Bullet - Baetis #14
#14
Olsen's Hare's Ear Blowtorch Barbless #20 - 28
#20
Top Secret Baetis #16
#16
Egan's Frenchie #12
#12
Hatch Chart
| Insect | Size | Activity | Prime Time |
|---|---|---|---|
| Blue-Winged Olive (Baetis) | #18-22 | Moderate | 10 AM - 1 PM |
| Midge | #20-24 | Heavy | 7 AM - 10 AM |
| Caddis | #16-20 | Light | 5 PM - 7 PM |
| Terrestrials (Ants) | #14-18 | Moderate | 11 AM - 2 PM |
| PMD | #18-20 | Light | 11 AM - 1 PM |
Best Time Window
- 6 AM - 9 AM: Prime midge and early BWO window before water temps climb — work the deeper pools and tail-outs with small nymphs.
- 10 AM - 1 PM: BWO and terrestrial overlap on sunny flats — switch to a dry fly and target rising fish in the slower meadow sections.
- 5 PM - 7 PM: Evening caddis activity in the riffles; fish the pocket water with a CDC Caddis before the storm system moves in tonight.
Guide's Tip
From the benchWith water at 70°F, your best window is the first two hours of daylight before thermals from the geothermal vents push temperatures up. Focus on the cooler tributary confluences and shaded bends where browns are staging ahead of fall spawn. Tonight's storm system is likely to drop temps and could trigger a strong BWO hatch Monday morning — if you can fish post-storm, get there early and go small with a #22 Parachute BWO or Juju Baetis in the flat meadow water. Keep your approach low and your casts upstream; these fish see a lot of pressure and spook easily in the clear, slow currents.
Main Species
Brown Trout
Rainbow Trout
Brook Trout
