day degrees The departure of the average daily temperature from a defined base, e.g. 4°C, the minimum recognized temperature for the growth of many plant species. The number of day degrees may be totalled to assess the accumulated warmth of a particular year's growing season for crops. See also ACCUMULATED TEMPERATURE; AGROMETEOROLOGY; and MONTH DEGREES.

day degrees The departure of the average daily temperature from a defined base (e.g. the minimum recognized temperature for the growth of a plant species). The number of day degrees may be totalled to assess the accumulated warmth of a particular year's growing season for crops. See also accumulated temperature; agrometeorology; and month degrees.

day degrees The departure of the average daily temperature from a defined base (e.g. the minimum recognized temperature for the growth of a plant species). The number of day degrees may be totalled to assess the accumulated warmth of a particular year's growing season for crops. See also ACCUMULATED TEMPERATURE; AGROMETEOROLOGY; and MONTH DEGREES.

de·gree day • n. a unit used to determine the heating requirements of buildings, representing a fall of one degree below a specified average outdoor temperature (usually 18°C or 65°F) for one day.