Bighorn River At Bridge, At St. Xavier
Bighorn River · Rockies · USGS gage 06287800
Coldwater (summer mean 14.8°C — prime coldwater).
Water
60°F
Flow
1,690 cfs
Air
79°F
Sky
0%
Pressure
29.81 in
Wind
5 mph
Predicted hatches · 2026-07-31
ConfirmedPale Morning DunEphemerella spp.1.00
Model says likely and 3 recent reports confirm it. water 15.4°C (60°F) sits in the prime band (13-18°C); peak season; 8 days sustained ≥12°C; watch late morning to early afternoon.
reports: Fly Fishing Bozeman — Bighorn Report, Yellow Dog — Bighorn River Reports, Yellow Dog — Bighorn River Reports
flies: PMD Comparadun #16-18, Sparkle Dun, Pheasant Tail #16
ConfirmedSpotted / Summer CaddisHydropsyche spp.1.00
Model says likely and 2 recent reports confirm it. water 15.4°C (60°F) sits in the prime band (14-19°C); peak season; 8 days sustained ≥12°C; watch evening, last hour of light.
flies: Elk Hair Caddis #14-16, Iris Caddis, X-Caddis
ReportedHopper / TerrestrialsAcrididae (grasshoppers)0.36
1 report say it's happening, though conditions are lukewarm. water 15.4°C (60°F) is warming toward the prime band (17-24°C); shoulder of the season; warm sun favors it; watch warm, breezy afternoons.
reports: Yellow Dog — Bighorn River Reports
flies: Morrish Hopper #8-12, Chubby Chernobyl, Dave's Hopper
PredictedGolden StoneHesperoperla / Calineuria0.87
Predicted by conditions; no reports yet. water 15.4°C (60°F) sits in the prime band (14-18°C); peak season; 2 days sustained ≥13°C (wants 3); watch afternoon and evening.
flies: Chubby Chernobyl #8-10, Yellow Stimulator, Pat's Rubber Legs
PredictedSalmonflyPteronarcys californica0.50
Predicted by conditions; no reports yet. water 15.4°C (60°F) sits in the prime band (13-16°C); shoulder of the season; 8 days sustained ≥12°C; watch late morning through evening.
flies: Rogue Foam Salmonfly #4-6, Chubby Chernobyl, Pat's Rubber Legs
PredictedGreen DrakeDrunella spp.0.43
Predicted by conditions; no reports yet. water 15.4°C (60°F) is cooling past the prime band (11-15°C); shoulder of the season; 8 days sustained ≥10°C; watch midday, often cloudy.
flies: Green Drake Parachute #10-12, Cripple, Hares Ear #10
PredictedSulphurEphemerella dorothea / invaria0.43
Predicted by conditions; no reports yet. water 15.4°C (60°F) sits in the prime band (15-19°C); shoulder of the season; 2 days sustained ≥13°C (wants 3); watch evening, the last two hours of light.
flies: Sulphur Comparadun #16-18, Sulphur Spinner, Pheasant Tail
PredictedSlate Drake / IsonychiaIsonychia spp.0.42
Predicted by conditions; no reports yet. water 15.4°C (60°F) is warming toward the prime band (16-21°C); peak season; watch afternoon/evening; nymphs crawl to shore to emerge.
flies: Isonychia #10-12, Slate Drake, Leadwing Coachman
PREDICTED from the first-principles model only. Report-confirmed signal (fly-shop & forum reports) is the next milestone.