Montana ·
Yellowstone River Fly Fishing Report - October 4, 2026
YELLOWSTONE RIVER
ReportOCT 4 — 11, 2026
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Flow
1250CFS
Yellowstone River at Corwin Springs MT
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Water Temp
57°F
Updated 2026-10-03
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Weather
38–82°F
Mostly Clear
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Clarity
Clear
Check post-storm
Water is at 57°F and flowing a very fishable 1,250 CFS at Corwin Springs — down slightly from last week and crystal clear, putting trout in a confident, aggressive fall feeding mode. With Sunday's high near 80°F and light south winds, expect midday dry-fly opportunities to rival anything you'll see all season.
What's Working — Hot Flies
Egan's GTI Caddis - Olive #12
12
Bionic Hopper - Tan #12
12
Bionic Ant 2.0 - Black #16
16
Parachute - Blue Wing Olive #22
22
Top Secret Baetis #16
16
Egan's Thread Frenchie Jig - Olive #12
12
Olsen's Straggle Stone Brown Barbless #12
12
Tungsten Rainbow Warrior - Extra Heavy #14
14
Juju Baetis Tungsten #22
22
Coffey's CH Sparkle Minnow Sculpin #6
6
Tungsten Pat's Rubber Legs - Tan & Brown #6
6
Bionic Ant 2.0 - Brown #12
12
Hatch Chart
| Insect | Size | Activity | Prime Time |
|---|---|---|---|
| October Caddis | 8-10 | Heavy | 2 PM - 6 PM |
| Blue-Winged Olive (Baetis) | 20-22 | Moderate | 11 AM - 2 PM |
| Terrestrials (Ants) | 14-16 | Moderate | 10 AM - 3 PM |
| Grasshoppers | 10-12 | Light | 12 PM - 4 PM |
| Midges | 20-22 | Light | 8 AM - 10 AM |
Best Time Window
- 7 AM - 9:30 AM: Early nymphing with heavy stonefly and Frenchie patterns in deep runs before the sun hits the water — fish are tight to structure and feeding hard.
- 11 AM - 2 PM: BWO hatch window on slower flats and tailouts — watch for sipping risers and match with a Parachute BWO or Top Secret Baetis on fine tippet.
- 2 PM - 6 PM: Prime October caddis time — work the GTI Caddis on a dead-drift-to-swing through riffle-to-pool transitions and expect aggressive surface and near-surface takes from big browns.
Guide's Tip
From the benchWith flows at 1,250 CFS and water this clear, your leader game matters — drop to 5X or 6X fluorocarbon for nymphing and go to 6X for dry-fly work in the flats. During the afternoon October caddis push, position yourself at the tail of a riffle where it transitions into a pool and work the swing: cast across and slightly downstream, mend once to get a short dead-drift, then let the fly arc through the current and hang below you for a full three seconds before picking up. Browns will crush it on the swing. If you're not getting takes on the surface by 3 PM, switch to the Sparkle Minnow and work the deep bucket water — pre-spawn browns are stacking up and actively hunting.
Main Species
Yellowstone Cutthroat Trout
Brown Trout
Rainbow Trout
