Several web sites offer historical temperature data for free. The HxGN EAM Upload Utility may be used to load Historical Averages. As data is stored in tables, the Temperature Averages are calculated.
Temperature Average for each day is calculated:
(Temperature Minimum + Temperature Maximum) / 2
Degree Day values are calculated from the Temperature Average and the Reference Point for specified days of the year.
Calculation is performed in Fahrenheit or Celsius, as specified.