Freestone · Mixed · Montana

Big Hole River

A drift boat floats past wading fly anglers on the Big Hole River, with a steep pine-and-rock canyon wall behind, Montana.

The Big Hole comes down out of the Pioneer Mountains and people love it the way you love a place that's been good to you.

Prime · Rainbow Trout
Parachute Adams · 12-18
Primelive now
About as good as it gets
River steady at a fishable height. On the feed top to bottom — start on the rises with a dry, drop a nymph if they stay down.
90% confidence
What moved it
  • Level0.67 mLast reading 12h ago
  • Water temp17.4°C
  • ClarityClear
Today's fly
Parachute Adams
Parachute Adams12-18
High-confidence seasonal pick
Conditions on the water
Live gauge
Level
Steady
0.67 m
Last reading 12h ago
Water temp17.4°C
ClarityClear
Weather17°C
WindS 3 km/h
Pressure1019 hPa
Rain · recent0.5 mm
Rain · ahead0.0 mm

Live readings only. Trends shown where the gauge supports them.

Water temperature for Rainbow Trout
Ideal
17.4°Cideal 1018°C
0°14°28°
How to fish it · for Rainbow 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 insect activity could be better.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 3 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

Top nymph shown — see all 2 guilds with Pro.

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Beyond the hatch · worth watchingambient prey

Hatch predictions

Top prey shown — see all 2 with Pro.

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Evidence
ModelledModerate confidence

Modelled from regional ecology — no survey or occurrence data for this water yet.

Through the year
0–3 scale · July 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
Western Green DrakeHatch
2
2
Flav (Small Western Green Drake)Hatch
2
3
2
Mahogany DunHatch
2
2
American March BrownHatch
2
3
2

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

Ranked for today
Rainbow Trout fly box
Permits & access
Permit required — see local rules.
  • Montana licence
  • Summer hoot-owl (afternoon) closures are common on the lower river
  • Holds the last fluvial Arctic grayling in the lower 48 — handle with care.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Gallery · 3
  1. A drift boat floats past wading fly anglers on the Big Hole River, with a steep pine-and-rock canyon wall behind, Montana.
    Floating the Big Hole
  2. Fishing the Big Hole
    Fishing the Big Hole
  3. Terrain map of the venue
    Terrain map
About this water

The Big Hole comes down out of the Pioneer Mountains and people love it the way you love a place that's been good to you. Browns, rainbows, and brook trout, plus the rare fluvial Arctic grayling — the last river-dwelling population in the lower 48, which is reason enough to handle them like the relics they are. The salmonfly hatch brings a crowd. By late summer the lower river runs low and warm and goes under hoot-owl restrictions, so plan on mornings.

Under the surface

The Big Hole runs out of the high, wide valley that gives it its name — the 'big hole' the old trappers meant, a broad sweep of hayfield and willow under the Pioneer Mountains — and threads down through Wisdom and Wise River toward its meeting with the Beaverhead. It's a true freestone, snowmelt-fed and unregulated, swinging from braided meadow channels up top to a rocky canyon lower down. The upper river is the last refuge of the fluvial Arctic grayling in the lower forty-eight, a fish that has no business still being there and is. The bed is rounded freestone cobble, the lies in the riffles, undercut banks and willow corners. The river runs cold and high through June and can drop worryingly low and warm in a dry August. Wading is straightforward on cobble, with the usual care where the canyon pushes the water.

Wading: Low warm water late summer, pushy in the canyon

  • Mixed
  • Partly confined
  • Pool riffle
  • Step pool
Water quality · US Clean Water Act
  • Aquatic lifeImpaired
What this classification means

EPA ATTAINS assessment unit 'Big Hole River' (MT41D001_010), 2021 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Temperature, Habitat Alterations, Hydrologic Alteration, Metals Other Than 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) · MT41D001_010

The full read · show the working · for Rainbow Trout · confidence 90%
How the 81 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time60 × 13%7.8
Pressure75 × 7%5.3
Insect activity60 × 12%7.2
Conditions total= 81
Can you trust it?
Water temperaturelive gauge readinggauge
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
  • TroutThird Saturday of MayLast day of February
Related guides
Booking & contacts