Montana ·
Gallatin River Fly Fishing Report - August 16, 2026

GALLATIN RIVER
ReportAUG 16 — 23, 2026
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Flow
482CFS
Gallatin River near Gallatin Gateway, MT
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Water Temp
—
Updated 2026-08-16
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Weather
47–81°F
Slight Chance Rain Showers
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Clarity
Clear
Check post-storm
Flow is running 482 cfs at 1.61 ft gauge height near Gallatin Gateway — slightly elevated from last week but still clean and very wadeable. Morning windows are prime before afternoon heat builds toward the 80°F high; a slight chance of afternoon thunderstorms (3–5 PM) could trigger a feeding flurry, so stay alert.
What's Working — Hot Flies

Bionic Hopper - Tan #12
#12

Bionic Hopper - Purple #12
#12

Bionic Ant 2.0 - Black #16
#16

Bionic Ant 2.0 - Brown #12
#12

Egan's GTI Caddis - Olive #12
#12

Parachute - Blue Wing Olive #22
#22

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

Egan's Frenchie #12
#12

Blowtorch - Hare's Ear #12
#12

Juju Baetis Tungsten #22
#22

Olsen's Straggle Stone Brown Barbless #12
#12

Top Secret Baetis #16
#16
Hatch Chart
| Insect | Size | Activity | Prime Time |
|---|---|---|---|
| Spruce Moth | 12-14 | Moderate | 9 AM - 2 PM |
| Grasshopper / Terrestrials | 10-12 | Moderate | 11 AM - 3 PM |
| Ants | 14-16 | Moderate | 10 AM - 2 PM |
| Baetis (BWO) | 20-22 | Light | 3 PM - 6 PM |
| Caddis | 16-18 | Light | 7 AM - 10 AM |
| Midge | 20-22 | Light | 7 AM - 9 AM |
Best Time Window
- 7 AM - 10 AM: Prime dry fly window — hoppers, ants, and caddis on canyon pocket water before the sun fully hits.
- 10 AM - 1 PM: Nymph the deeper slots and boulder seams as surface activity slows; Frenchies and Straggle Stones shine.
- 3 PM - 6 PM: Watch for afternoon storm clouds to trigger a BWO hatch on tailouts; switch to small dries and emergers.
Guide's Tip
From the benchGet on the water by 7 AM and focus your dry fly game on the canyon pocket water — fish are actively feeding before the sun hits the water and temperatures climb. Slap hoppers and ants tight to the bank structure and undercut rocks, then let the fly dead-drift without any mending for at least 3–4 feet before picking up. If afternoon thunderstorms materialize around 3–5 PM, don't leave — that low-light window often triggers a short but intense BWO hatch on the tailouts; switch to a #22 Parachute BWO and work the flat water below riffles. Keep a close eye on water temperature in the lower valley sections and plan to wrap up fishing there well before midday.
Main Species
Brown Trout
Rainbow Trout
Westslope Cutthroat Trout
