Alameda Creek below Welch Creek near Sunol
Alameda Creek · Sierra / West · USGS gage 11173575
Trout (marginal) (summer mean 18.9°C — trout, warm in summer).
Water
65°F
Flow
7 cfs
Air
60°F
Sky
0%
Pressure
29.96 in
Wind
10 mph
Predicted hatches · 2026-07-31
PredictedSpotted / Summer CaddisHydropsyche spp.1.00
Predicted by conditions; no reports yet. water 18.3°C (65°F) sits in the prime band (14-19°C); peak season; 7 days sustained ≥12°C; watch evening, last hour of light.
flies: Elk Hair Caddis #14-16, Iris Caddis, X-Caddis
PredictedSlate Drake / IsonychiaIsonychia spp.1.00
Predicted by conditions; no reports yet. water 18.3°C (65°F) sits in the prime band (16-21°C); peak season; 7 days sustained ≥14°C; watch afternoon/evening; nymphs crawl to shore to emerge.
flies: Isonychia #10-12, Slate Drake, Leadwing Coachman
PredictedPale Morning DunEphemerella spp.0.90
Predicted by conditions; no reports yet. water 18.3°C (65°F) is cooling past the prime band (13-18°C); peak season; 7 days sustained ≥12°C; watch late morning to early afternoon.
flies: PMD Comparadun #16-18, Sparkle Dun, Pheasant Tail #16
PredictedGolden StoneHesperoperla / Calineuria0.90
Predicted by conditions; no reports yet. water 18.3°C (65°F) is cooling past the prime band (14-18°C); peak season; 7 days sustained ≥13°C; watch afternoon and evening.
flies: Chubby Chernobyl #8-10, Yellow Stimulator, Pat's Rubber Legs
PredictedHopper / TerrestrialsAcrididae (grasshoppers)0.56
Predicted by conditions; no reports yet. water 18.3°C (65°F) sits in the prime band (17-24°C); shoulder of the season; 7 days sustained ≥14°C; wind puts terrestrials in play; watch warm, breezy afternoons.
flies: Morrish Hopper #8-12, Chubby Chernobyl, Dave's Hopper
PredictedTricoTricorythodes spp.0.50
Predicted by conditions; no reports yet. water 18.3°C (65°F) sits in the prime band (16-21°C); shoulder of the season; 7 days sustained ≥15°C; watch early morning spinner falls.
flies: Trico Spinner #20-24, CDC Trico, Griffith's Gnat
PredictedSulphurEphemerella dorothea / invaria0.50
Predicted by conditions; no reports yet. water 18.3°C (65°F) sits in the prime band (15-19°C); shoulder of the season; 7 days sustained ≥13°C; watch evening, the last two hours of light.
flies: Sulphur Comparadun #16-18, Sulphur Spinner, Pheasant Tail
PredictedLight CahillStenacron / Stenonema0.50
Predicted by conditions; no reports yet. water 18.3°C (65°F) sits in the prime band (16-20°C); shoulder of the season; 7 days sustained ≥15°C; watch dusk.
flies: Light Cahill #14-16, Cream Cahill, Cahill Spinner
PredictedHexagenia (Hex)Hexagenia limbata0.17
water 18.3°C (65°F) is warming toward the prime band (19-23°C); shoulder of the season; 7 days sustained ≥18°C; bright moon — night activity; watch after dark — the famous night hatch.
flies: Hex Dun #4-8, Hex Nymph, Hex Spinner
PREDICTED from the first-principles model only. Report-confirmed signal (fly-shop & forum reports) is the next milestone.