Water temperature for Rainbow Trout
Warm — slow18°C est.ideal 10–18°C
0°14°28°
How to fish it · for Rainbow Trout
When
Season runs 1 June to 14 October — deliberately late, because the Lys carries too much glacial meltwater to fish well before then. Mornings are clearer than afternoons once the glacier gets going for the day.
Where
The three-kilometre reserve above Gressoney-La-Trinité — pocket water and pools typical of a Monte Rosa torrent, restocked weekly.
Method
Bait, spinning or fly all permitted; no catch-and-release requirement. Minimum size 25cm, six fish per permit, up to three permits a day.
Kit
9 ft #5/6, floating line — nothing needs to be delicate here, the water is rarely gin-clear.
Why this works
Water at 18.2°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayPeak at 5pm
Hatch predictions
Today's headline hatch shown — see all 9 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 2 with Pro.
Start free trial14-day free trial. Cancel anytime.
Through the year
0–3 scale · July highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Large Dark OliveHatch
1
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1
Autumn OliveHatch
1
2
1
GrannomHatch
1
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Rainbow Trout fly box
Top
6-10 · Pattern
Swing, sub-surface
Permits & access
Permit required — see local rules.
- Managed tourist reserve — daily permit required, weekly stocking
- Minimum size 25cm, 6 fish per permit, maximum 3 permits per angler per day
- No catch-and-release requirement.
What's coming
Plan ahead
5-day outlook
Water here around 18°C. Nothing cooler within range — carry a thermometer.
The full read · show the working · for Rainbow Trout · confidence 90%
How the 39 is built — score × weight = contribution
Temperature93 × 28%26.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time65 × 13%8.5
Pressure75 × 7%5.3
Insect activity62 × 12%7.4
Conditions total= 80
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Rainbow trout 2026-06-01 → 2026-10-14
Related guides
Booking & contacts
Lys
Water temperature for Rainbow Trout
Warm — slow18°C est.ideal 10–18°C
0°14°28°
How to fish it · for Rainbow Trout
When
Season runs 1 June to 14 October — deliberately late, because the Lys carries too much glacial meltwater to fish well before then. Mornings are clearer than afternoons once the glacier gets going for the day.
Where
The three-kilometre reserve above Gressoney-La-Trinité — pocket water and pools typical of a Monte Rosa torrent, restocked weekly.
Method
Bait, spinning or fly all permitted; no catch-and-release requirement. Minimum size 25cm, six fish per permit, up to three permits a day.
Kit
9 ft #5/6, floating line — nothing needs to be delicate here, the water is rarely gin-clear.
Why this works
Water at 18.2°C — above the brown trout caution line (18°C). Fish dawn or dusk only. Land it fast, wet hands, no air shots.
Hatch timeline · todayPeak at 5pm
Hatch predictions
Today's headline hatch shown — see all 9 active hatches hour by hour with Pro.
Start free trial14-day free trial. Cancel anytime.
Beyond the hatch · worth watchingambient prey
Hatch predictions
Top prey shown — see all 2 with Pro.
Start free trial14-day free trial. Cancel anytime.
Through the year
0–3 scale · July highlighted
J
F
M
A
M
J
J
A
S
O
N
D
Large Dark OliveHatch
1
2
2
1
Blue Winged OliveHatch
1
2
2
2
2
1
Autumn OliveHatch
1
2
1
GrannomHatch
1
1
Numbers are intensity 0 (none) to 3 (peak) — a guide, not a guarantee.
Ranked for today
Rainbow Trout fly box
Top
6-10 · Pattern
Swing, sub-surface
Permits & access
Permit required — see local rules.
- Managed tourist reserve — daily permit required, weekly stocking
- Minimum size 25cm, 6 fish per permit, maximum 3 permits per angler per day
- No catch-and-release requirement.
What's coming
Plan ahead
5-day outlook
Water here around 18°C. Nothing cooler within range — carry a thermometer.
The full read · show the working · for Rainbow Trout · confidence 90%
How the 39 is built — score × weight = contribution
Temperature93 × 28%26.0
Flow80 × 22%17.6
Clarity85 × 18%15.3
Feeding Time65 × 13%8.5
Pressure75 × 7%5.3
Insect activity62 × 12%7.4
Conditions total= 80
Can you trust it?
Water temperatureair-to-water estimateestimated
Level / flowon-river gaugeobserved
What would change the calculation
The dawn and dusk windows score higher than the midday lull.
Directions
Seasons & zones
- Rainbow trout 2026-06-01 → 2026-10-14
Related guides
Booking & contacts