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

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Big Wood River near Ketchum

Big Wood River · Rockies · USGS gage 13135500

Coldwater (summer mean 12.8°C — prime coldwater).

Water
50°F
Flow
55 cfs
Air
44°F
Sky
0%
Pressure
30.01 in
Wind
2 mph
Predicted hatches · 2026-09-15
PredictedBlue-Winged OliveBaetis spp.0.50
Predicted by conditions; no reports yet. water 9.8°C (50°F) sits in the prime band (6-11°C); shoulder of the season; watch midday, especially overcast afternoons.
flies: BWO Sparkle Dun #18-22, RS2, Pheasant Tail #18
PredictedMidgeChironomidae0.50
Predicted by conditions; no reports yet. water 9.8°C (50°F) sits in the prime band (1-10°C); shoulder of the season; watch midday, especially cold months.
flies: Zebra Midge #18-22, Griffith's Gnat, Disco Midge

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