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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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Weber River At Gateway

Weber River · Rockies · USGS gage 10136500

Trout (marginal) (summer mean 16.6°C — trout, warm in summer).

Water
55°F
Flow
297 cfs
Air
82°F
Sky
0%
Predicted hatches · 2026-06-16
PredictedGreen DrakeDrunella spp.1.00
Predicted by conditions; no reports yet. water 12.9°C (55°F) sits in the prime band (11-15°C); peak season; watch midday, often cloudy.
flies: Green Drake Parachute #10-12, Cripple, Hares Ear #10
PredictedSalmonflyPteronarcys californica0.90
Predicted by conditions; no reports yet. water 12.9°C (55°F) is warming toward the prime band (13-16°C); peak season; watch late morning through evening.
flies: Rogue Foam Salmonfly #4-6, Chubby Chernobyl, Pat's Rubber Legs
PredictedPale Morning DunEphemerella spp.0.45
Predicted by conditions; no reports yet. water 12.9°C (55°F) is warming toward the prime band (13-18°C); shoulder of the season; watch late morning to early afternoon.
flies: PMD Comparadun #16-18, Sparkle Dun, Pheasant Tail #16
PredictedEastern Green DrakeEphemera guttulata0.45
Predicted by conditions; no reports yet. water 12.9°C (55°F) is warming toward the prime band (14-18°C); peak season; watch evening; the spinner (Coffin Fly) falls at dusk.
flies: Green Drake #8-10, Coffin Fly Spinner, Drake Emerger
PredictedMidgeChironomidae0.26
water 12.9°C (55°F) is cooling past 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
PredictedSpotted / Summer CaddisHydropsyche spp.0.23
water 12.9°C (55°F) is warming toward the prime band (14-19°C); shoulder of the season; watch evening, last hour of light.
flies: Elk Hair Caddis #14-16, Iris Caddis, X-Caddis
PredictedMarch Brown (Eastern)Maccaffertium vicarium0.23
water 12.9°C (55°F) is warming toward the prime band (14-18°C); shoulder of the season; watch sporadic through the day, midday into afternoon.
flies: March Brown #10-12, Hare's Ear, Spinner

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