Calculating Growing Degree Days

Learn how to calculate growing degree days for a more accurate prediction of when things bloom and more successful honey production. 

September 17, 2012

By Kim Flottum 

There’s a simple technique for starting your own growing degree days (GDD) database, but first a ground rule. Plants essentially don’t grow if the ambient high temperature for the day is more than 86°F (30°C), or the low temperature for the day is below 50°F (10°C), so these two extremes must be noted in all calculations.

The basics of calculating growing degree days is as such:



Using various resources or media (such as weather websites or networks), find the high temperature for the day, add it to the low temperature for the day, and calculate the average by dividing by two. Subtract that number from the base temperature you are using (which is 50°F [10°C]).