Freestone · Mixed · Montana, US

Boulder River

Fast whitewater cascading through a boulder-strewn canyon on the upper Boulder River in Sweet Grass County, Montana, flanked by conifer forest
Today · About as good as it gets
Sculpin Streamer
Forecast · Today
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.
90% projected
Today's fly
Sculpin Streamer
Sculpin Streamer
Conditions on the water · Today
Live gauge
Level
Falling
0.36 m
Dropping after lift
Water temp9.2°C
ClarityClearing
Weather13°C
WindN 19 km/h
Pressure1020 hPa
Rain · recent0.0 mm
Rain · ahead0.0 mm

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

Water temperature for Cutthroat Trout
Ideal
9°C est.ideal 9–15°C
0°14°28°
How to fish it · for Cutthroat 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.
Likely species
Mayflies
Gammarids
Hatch timeline · todayPeak at 11 Uhr

12 Uhr(now) — Western Blue-Winged Olive

Stage: On emergersApproach: Emerger or dryActivity: 40%
Also:Black Midge29%
Peak emergence window5 food groups active

Peak activity at 11 Uhr — Western Blue-Winged Olive (Western Blue-Winged Olive, Peak emergence window)

Sub-surface · on the nymphunder the surface

Hatch predictions

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Beyond the hatch · worth watchingambient prey(1)

Hatch predictions

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Evidence
Records-basedModerate confidence

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

Through the year
0–3 scale · October 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
Fly box · Cutthroat Trout
SD
Sex Dungeon
2-6 · Pattern
Proven pattern for this period
Permits & access
Permit required — see local rules.
  • Montana licence
  • Yellowstone/westslope cutthroat are native here — handle and release them gently.
What's coming
Plan ahead
5-day outlook
Other water nearby · 5
Paradise Valley Spring Creeks
30 km
Rainbow trout · Brown trout
Shields River
46 km
Brown trout · Rainbow trout
Yellowstone River
50 km
83
Brown trout · Rainbow trout · Cutthroat trout
Stillwater River
60 km
79
Rainbow trout · Brown trout · Cutthroat trout
Gallatin River
88 km
Rainbow trout · Brown trout
Gallery · 2
  1. Fast whitewater cascading through a boulder-strewn canyon on the upper Boulder River in Sweet Grass County, Montana, flanked by conifer forest
    Whitewater on the upper Boulder River, Sweet Grass County, Montana
  2. Terrain map of the venue
    Terrain map
Water quality · US Clean Water Act
  • Aquatic life: Impaired
What this classification means

EPA ATTAINS assessment unit 'Boulder River' (MT43B004_132), 2021 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Nutrients, Habitat Alterations, 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) · MT43B004_132

The full read · show the working · for Cutthroat Trout · confidence 90%
How the 83 is built — score × weight = contribution
Temperature100 × 28%28.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time70 × 13%9.1
Pressure75 × 7%5.3
Insect activity63 × 12%7.6
Conditions total= 83
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
Directions
Apple MapsGoogle Maps
Seasons & zones
  • Trout Dritter Saturday im May → Letzter day of February
Related guides
Euro Nymphingsubsurface methods
Booking & contacts