Water temperature for Rainbow Trout
Warm — slow23.1°Cideal 10–18°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 23.1°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 2 with Pro.
Start free trial14-day free trial. Cancel anytime.
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
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.
- 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
Water here at 23.1°C. Nothing cooler within range.
Gallery · 2
Visitors fishing the Firehole River Terrain map
The full read · show the working · for Rainbow Trout · confidence 90%
How the 4 is built — score × weight = contribution
Temperature2 × 28%0.6
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time55 × 13%7.2
Pressure75 × 7%5.3
Insect activity39 × 12%4.7
Limiting factor: Water temperature (23.1°C) is outside Rainbow Trout's preferred range (10–18°C)= 51
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.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- TroutSaturday of Memorial Day weekend → First Sunday in November
Related guides
Booking & contacts
Firehole River
Water temperature for Rainbow Trout
Warm — slow23.1°Cideal 10–18°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 23.1°C. This is the line where catch-and-release kills brown trout. Do not fish for them today.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 2 with Pro.
Start free trial14-day free trial. Cancel anytime.
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
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.
- 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
Water here at 23.1°C. Nothing cooler within range.
Gallery · 2
Visitors fishing the Firehole River Terrain map
The full read · show the working · for Rainbow Trout · confidence 90%
How the 4 is built — score × weight = contribution
Temperature2 × 28%0.6
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time55 × 13%7.2
Pressure75 × 7%5.3
Insect activity39 × 12%4.7
Limiting factor: Water temperature (23.1°C) is outside Rainbow Trout's preferred range (10–18°C)= 51
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.
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- TroutSaturday of Memorial Day weekend → First Sunday in November
Related guides
Booking & contacts