Growing degree days

The growing degree days index represents a measure of the accumulated heat available for vegetation growth. It is calculated as the accumulated sum over the year of the daily mean temperature exceedances of a base threshold (see the ETC-CCA Technical Paper for details). A base temperature of +5 °C is considered as representative for most European crops. Other definitions of the index are possible, including variations of the minimum temperature, the use of an upper temperature threshold, and restrictions to a given growing season.