Green River Near Green River
Green River · Rockies · USGS gage 09217000
Trout (marginal) (summer mean 20.2°C — trout, warm in summer).
Water
71°F
Flow
499 cfs
Air
80°F
Sky
10%
Predicted hatches · 2026-06-16
PredictedHexagenia (Hex)Hexagenia limbata0.73
Predicted by conditions; no reports yet. water 21.4°C (71°F) sits in the prime band (19-23°C); peak season; 1 day sustained ≥18°C (wants 3); watch after dark — the famous night hatch.
flies: Hex Dun #4-8, Hex Nymph, Hex Spinner
PredictedLight CahillStenacron / Stenonema0.53
Predicted by conditions; no reports yet. water 21.4°C (71°F) is cooling past the prime band (16-20°C); peak season; 8 days sustained ≥15°C; watch dusk.
flies: Light Cahill #14-16, Cream Cahill, Cahill Spinner
PredictedSlate Drake / IsonychiaIsonychia spp.0.43
Predicted by conditions; no reports yet. water 21.4°C (71°F) is cooling past the prime band (16-21°C); shoulder of the season; 8 days sustained ≥14°C; watch afternoon/evening; nymphs crawl to shore to emerge.
flies: Isonychia #10-12, Slate Drake, Leadwing Coachman
PredictedSulphurEphemerella dorothea / invaria0.20
water 21.4°C (71°F) is cooling past the prime band (15-19°C); peak season; 8 days sustained ≥13°C; watch evening, the last two hours of light.
flies: Sulphur Comparadun #16-18, Sulphur Spinner, Pheasant Tail
PREDICTED from the first-principles model only. Report-confirmed signal (fly-shop & forum reports) is the next milestone.