About Growing Degree Hours
Growing degree hours (GDH) are a weighted measurement of the temperatures to which a tree is exposed, based on the idea that trees have an optimum temperature for growth and that temperatures far above or below that optimum temperature have a greater impact than temperatures just above or just below it. UC Davis’s Harvest Prediction Model calculates GDH values based on the equation of Anderson et al., 1986 and temperature readings collected by the more than 100 CIMIS weather stations throughout the state.