Sf Boise River At Neal Bridge near Arrowrock Dam
Sf Boise River · Rockies · USGS gage 13192200
Coldwater (summer mean 12.9°C — prime coldwater).
Water
58°F
Flow
500 cfs
Air
69°F
Sky
100%
Pressure
30.10 in
Wind
4 mph
Predicted hatches · 2026-09-18
PredictedSpotted / Summer CaddisHydropsyche spp.0.50
Predicted by conditions; no reports yet. water 14.7°C (58°F) sits in the prime band (14-19°C); shoulder of the season; 8 days sustained ≥12°C; watch evening, last hour of light.
flies: Elk Hair Caddis #14-16, Iris Caddis, X-Caddis
PredictedSlate Drake / IsonychiaIsonychia spp.0.35
water 14.7°C (58°F) is warming toward the prime band (16-21°C); peak season; 2 days sustained ≥14°C; 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.