Introducing the Thermal Calendars tool
Mon, Mar 09, 2026
Temperature is an important factor governing when seasonal events happen in many plant and animal species. For many species, events like leaf-out, flowering, and egg hatch are triggered when a specific amount of heat has accumulated since the start of the year. We typically measure accumulated heat in growing degree days (GDDs). The Thermal Calendars tool indicates when particular GDD levels (or thresholds) of accumulated warmth are met each year in the northeastern U.S. Local resource managers can use the tool to determine when problematic insect pests are expected to enter particular life stages when they may cause the most damage or are most readily controlled.
