Freestone · Mixed · Montana

Yellowstone River

Yellowstone River venue image

Through Paradise Valley the Yellowstone is big, honest freestone water — browns, rainbows, and Yellowstone cutthroat all sharing the same long runs and bank seams.

Poor · Brown Trout
Parachute Adams · 12-18
Poorlive now
Not the day for it
River temperature is the limiting factor today, not the flow. This is not the day to push it. Check the thermal advice above before you head out.
80% confidence
What moved it
  • Level1.02 mDropping after lift
  • Water temp20.5°C
  • ClarityClear
Today's fly
Parachute Adams
Parachute Adams12-18
High-confidence seasonal pick
Conditions on the water
Live gauge
Level
Steady
1.02 m
Dropping after lift
Water temp20.5°C
ClarityClear
Weather25°C
WindE 5 km/h
Pressure1014 hPa
Rain · recent0.2 mm
Rain · ahead0.0 mm

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

Water temperature for Brown Trout
Warm — slow
20.5°Cideal 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
Water at 20.5°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayQuiet day

Hatch predictions

Today's headline hatch shown — see all 2 active hatches hour by hour with Pro.

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Sub-surface · on the nymphunder the surface

Hatch predictions

See the full sub-surface read 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
Brown Trout fly box
Permits & access
Permit required — see local rules.
  • Montana licence
  • Frequently unfishable through June runoff
  • Handle native cutthroat gently and release.
What's coming
Plan ahead
5-day outlook
Water here at 20.5°C. Nothing cooler within range.
Gallery · 1
  1. Terrain map of the venue
    Terrain map
About this water

Through Paradise Valley the Yellowstone is big, honest freestone water — browns, rainbows, and Yellowstone cutthroat all sharing the same long runs and bank seams. The Mother's Day caddis and the post-runoff salmonfly and golden stone hatches are the events people drive for. The catch is late spring, when a long, muddy runoff window owns the river and there's nothing to do but wait it out.

Under the surface

The Yellowstone is the longest undammed river left in the lower forty-eight, and it earns the title the hard way — from its source south of the park, through Yellowstone Lake, over the two great falls and down the Grand Canyon of the Yellowstone with its yellow rhyolite walls, then out across Paradise Valley beneath the Absarokas toward Livingston and the plains. The fishing river is the freestone below the park: a big, brawling, cottonwood-lined flood that rises hard and brown with the June snowmelt and drops into shape by July. The bed is rounded volcanic and granitic cobble, the lies in the riffle corners and along the cut banks. This is native cutthroat water at heart, sharing the run now with browns and rainbows. Wading is honest work on slick freestone, and the river runs higher and faster than your eye keeps telling you.

Wading: Fast, high water over slick freestone

  • Mixed
  • Unconfined
  • Pool riffle
  • Large river
Water quality · US Clean Water Act
  • Aquatic lifeImpaired
What this classification means

EPA ATTAINS assessment unit 'Yellowstone River' (MT43B003_010), 2021 Integrated Report. Aquatic Life use: Not Supporting. Listed impairment causes: Habitat Alterations. 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) · MT43B003_010

The full read · show the working · for Brown Trout · confidence 80%
How the 24 is built — score × weight = contribution
Temperature19 × 28%5.3
Flow80 × 22%17.6
Clarity95 × 18%17.1
Feeding Time40 × 13%5.2
Pressure80 × 7%5.6
Insect activity56 × 12%6.7
Limiting factor: Water temperature (20.5°C) is outside Brown Trout's preferred range (10–16°C)= 58
Can you trust it?
Water temperaturelive gauge readinggauge
Level / flowon-river gaugeobserved
Prey activitymodelled from regional profilemodelled
What would change the calculation
Cooler water — back toward the 10–16 °C ideal band — would lift the score and ease welfare.
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