A corn growing degree day (GDD) is an index used to
express crop maturity. The index is computed by subtracting a base temperature of 50°F
from the average of the maximum and minimum temperatures for the day. Minimum temperatures
less than 50°F are set to 50, and maximum temperatures greater than 86°F
are set to 86. These substitutions indicate that no appreciable growth is detected with
temperatures lower than 50 or greater than 86.