Flathead River At Columbia Falls
Flathead River · Rockies · USGS gage 12363000
Coldwater (summer mean 13.8°C — prime coldwater; very large river (17,700 cfs)).
Water
59°F
Flow
6,320 cfs
Air
n/a
Sky
n/a
Pressure
n/a
Wind
n/a
Predicted hatches · 2026-08-03
PredictedSpotted / Summer CaddisHydropsyche spp.1.00
Predicted by conditions; no reports yet. water 15.0°C (59°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
PredictedPale Morning DunEphemerella spp.0.50
Predicted by conditions; no reports yet. water 15.0°C (59°F) sits in the prime band (13-18°C); shoulder of the season; 8 days sustained ≥12°C; watch late morning to early afternoon.
flies: PMD Comparadun #16-18, Sparkle Dun, Pheasant Tail #16
PredictedHopper / TerrestrialsAcrididae (grasshoppers)0.33
water 15.0°C (59°F) is warming toward the prime band (17-24°C); peak season; 8 days sustained ≥14°C; watch warm, breezy afternoons.
flies: Morrish Hopper #8-12, Chubby Chernobyl, Dave's Hopper
PredictedSlate Drake / IsonychiaIsonychia spp.0.25
water 15.0°C (59°F) is warming toward 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
PREDICTED from the first-principles model only. Report-confirmed signal (fly-shop & forum reports) is the next milestone.