Q.Freshwater Trout & Hatches
What water temperature triggers mayfly hatches?
A.
Most mayfly hatches start when water temperatures hit species-specific thresholds: BWOs around 45-55°F, sulphurs at 55-65°F, green drakes at 60-65°F, tricos at 60-70°F. Sustained water temperature in the trigger range produces the heaviest emergences; brief temperature spikes don't.
Hatch calendar pages cover species-specific temperature triggers and historical timing on specific rivers.