Freestone · Mixed · Wyoming, US

Firehole River

Two anglers casting fly rods while wading the Firehole River at golden hour, Yellowstone National Park.

The Firehole is a strange, lovely meadow river that slides past geysers and hot springs inside Yellowstone NP, holding browns and rainbows in some of the oddest country a trout ever lived in.

Tomorrow · A proper day on the water
Sculpin Streamer
Forecast · Tomorrow
A proper day on the water
A proper day for it. Work the seams with an upstream nymph, switch to the dry when they show.
75% projected
Today's fly
Sculpin Streamer
Sculpin Streamer
Conditions on the water · Tomorrow
Live gauge
Level
Steady
0.90 m
Water temp8.9°C
ClarityClear
Weather11°C
WindN 15 km/h
Pressure1014 hPa
Rain · recent0.7 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 Rainbow Trout
Cool — slow
9°C est.ideal 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
Water at 20.8°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Likely species
Hatch timeline · tomorrowPeak at 9pm

12pm(now) Mahogany Dun

Stage: On emergersApproach: Emerger or dryActivity: 60%
Also:Black Midge56%
Peak emergence window5 food groups active

Peak activity at 9pm — Brown Dun (Brown Dun, 4 food groups active)

Sub-surface · on the nymphunder the surface

Hatch predictions

See the full sub-surface read with Pro.

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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
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
Rainbow Trout fly box
SD
Sex Dungeon
2-6 · Pattern
Proven pattern for this period
Permits & access
Permit required — see local rules.
  • Yellowstone NP licence and special regulations
  • Geothermal input pushes summer water temperatures too high to fish ethically — it is a spring and autumn river.
What's coming
Plan ahead
5-day outlook
Cooler water nearby · 4
Water here at 20.8°C — the fishing's alive, but these are cooler if you'd rather rest the warm water.
Gallery · 2
  1. Two anglers casting fly rods while wading the Firehole River at golden hour, Yellowstone National Park.
    Visitors fishing the Firehole River
  2. Terrain map of the venue
    Terrain map
About this water

The Firehole is a strange, lovely meadow river that slides past geysers and hot springs inside Yellowstone NP, holding browns and rainbows in some of the oddest country a trout ever lived in. It's a spring and autumn river by necessity — all that geothermal water shoves summer temperatures too high to fish in good conscience, so you leave it alone in the heat. Park special regulations apply. Swing a soft-hackle through the geyser-basin flats in the cool months and let high summer belong to the river.

Under the surface

The Firehole is the strangest trout river in America, and possibly the most beautiful. It runs through the heart of Yellowstone's geyser country, and the hot water of the basins — Old Faithful, Midway, the Lower Geyser Basin — bleeds into it until the river is literally warmed by the earth. Steam drifts off the meadows; the bank may be a bubbling spring. The result is a smooth, clear, weed-rich meadow stream that fishes early and late in the season when other rivers run too cold, and shuts down in midsummer when the geyser heat pushes it too warm for the trout's comfort. The bed is volcanic sand and gravel over rhyolite. The browns and rainbows here are wild and well-educated. Wading is easy on firm footing — but mind the thermal ground at the edges, which is exactly as dangerous as it looks.

Wading: Scalding thermal ground at the banks

  • Mixed
  • Unconfined
  • Pool riffle
The full read · show the working · for Rainbow Trout · confidence 80%
How the 22 is built — score × weight = contribution
Temperature15 × 28%4.2
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time80 × 13%10.4
Pressure75 × 7%5.3
Insect activity41 × 12%4.9
Limiting factor: Water temperature (20.8°C) is outside Rainbow Trout's preferred range (10–18°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 10–18 °C ideal band — would lift the score and ease welfare.
Directions
Seasons & zones
  • Trout Saturday of Memorial Day weekendFirst Sunday in November
Related guides
Booking & contacts