Fly Fish ForecastBeta

Hatch predictions for 300+ US rivers — built from live water & weather, then confirmed against real fly-shop reports.

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San Juan River At Farmington

San Juan River · Rockies · USGS gage 09365000

Trout (marginal) (summer mean 19.1°C — trout, warm in summer).

Water
74°F
Flow
800 cfs
Air
89°F
Sky
1%
Predicted hatches · 2026-06-16
PredictedHexagenia (Hex)Hexagenia limbata0.87
Predicted by conditions; no reports yet. water 23.4°C (74°F) is cooling past the prime band (19-23°C); peak season; 5 days sustained ≥18°C; watch after dark — the famous night hatch.
flies: Hex Dun #4-8, Hex Nymph, Hex Spinner

PREDICTED from the first-principles model only. Report-confirmed signal (fly-shop & forum reports) is the next milestone.