Freestone · Mixed · Montana, US

Clark Fork

Wide view of a gravel road crossing the Clark Fork River on a bridge, with a road sign reading Clark Fork River, cottonwoods and mountains in the background

The Clark Fork is a river with a hard past — the upper reaches carried a century of mining poison out of Butte, and what you fish today is the product of an enormous cleanup.

Tomorrow · About as good as it gets
Pheasant Tail
Forecast · Tomorrow
About as good as it gets
On the feed top to bottom — start on the rises with a dry, drop a nymph if they stay down.
75% projected
Today's fly
Pheasant Tail
Pheasant Tail
Conditions on the water · Tomorrow
Live gauge
Level
Steady
0.43 m
Water temp12.2°C
ClarityClear
Weather14°C
WindN 8 km/h
Pressure1008 hPa
Rain · recent0.0 mm
Rain · ahead2.0 mm

The nearest gauge doesn't record temperatures, so we've estimated it — defer to the river keeper's advice.

Water temperature for Brown Trout
Ideal
12°C est.ideal 1016°C
0°14°28°
How to fish it · for Brown Trout
When
Nymphing can work through most of the day.
Where
Cover mixed depths.
Method
Start with tight-line nymphs and adjust if fish rise or drift higher.
Kit
9 ft #4 rod, floating line, 12 ft tapered leader to 4–5 lb fluoro tippet.
Why this works
Excellent — water temperature is right today, though time of day could be better.
Likely species
Hatch timeline · tomorrowPeak at 12pm

12pm(now) Mahogany Dun

Stage: On emergersApproach: Emerger or dryActivity: 95%
Also:Reed Smut54%
Peak emergence windowDegree-days at peak8 food groups active

Peak activity at 12pm — Mahogany Dun (Mahogany Dun, Peak emergence window)

Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 2 guilds with Pro.

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14-day free trial. Cancel anytime.

Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

Top prey shown — see all 2 with Pro.

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14-day free trial. Cancel anytime.

Evidence
Records-basedModerate confidence

Based on species-occurrence records, not local invertebrate surveys.

Through the year
0–3 scale · September highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Trout seasonSeason
2
1
1
2
2
2
2
2
2
2
Brown DunHatch
2
3
3
3
3
3
3
2
Western Green DrakeHatch
2
2
Flav (Small Western Green Drake)Hatch
2
3
2
Mahogany DunHatch
2
2

Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.

Ranked for today
Brown Trout fly box
SD
Sex Dungeon
2-6 · Pattern
Proven pattern for this period
Permits & access
Permit required — see local rules.
  • Montana licence
  • Check FWP for hoot-owl (afternoon) closures on the lower river in hot summers.
What's coming
Plan ahead
5-day outlook
Other water nearby · 3
Gallery · 2
  1. Wide view of a gravel road crossing the Clark Fork River on a bridge, with a road sign reading Clark Fork River, cottonwoods and mountains in the background
    The Clark Fork River, Powell County, Montana
  2. Terrain map of the venue
    Terrain map
About this water

The Clark Fork is a river with a hard past — the upper reaches carried a century of mining poison out of Butte, and what you fish today is the product of an enormous cleanup. Below Missoula it's grown back into a big, broad freestone full of browns and rainbows that eat trico and baetis and a fine fall caddis. It's a float river in its lower reaches and a wade river up high. Like most things around here it goes brown in June runoff and then settles into a long, generous summer and fall.

  • Mixed
Water quality · US Clean Water Act
  • Aquatic lifeImpaired
  • RecreationImpaired
What this classification means

Recreation: Bacteria/pathogen advisory — mind wading cuts and immersion.

EPA ATTAINS assessment unit 'Clark Fork River' (MT76E001_010), 2021 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Nutrients, Algal Growth, Habitat Alterations, Metals Other Than Mercury, Mercury. This is a Clean Water Act assessment-unit classification (the US analogue of WFD), not a live reading.

Status is for the Clean Water Act assessment unit covering this reach.

EPA ATTAINS (Clean Water Act) · MT76E001_010

The full read · show the working · for Brown Trout · confidence 90%
How the 84 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time60 × 13%7.8
Pressure80 × 7%5.6
Insect activity62 × 12%7.4
Conditions total= 84
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
  • Trout Third Saturday of MayLast day of February
Related guides
Booking & contacts