Degree Day Calculations

There are five types of degree day calculations represented in the Point Forecast API.

(These are assuming usage of degrees Fahrenheit.)

CDD1

Cooling degree days. This is the standard method of subtracting 65 using the average of the daily high temperature and daily low temperature.

CDD1 = (Daily High Temp + Daily Low Temp) / 2.0 – 65

CDD2

Cooling Degree Days (Experimental). This method subtracts the 65 from the average of all of the 24 hourly temperatures.

CDD2 = Average Temp for the Day – 65

HDD1

Heating degree days. This is the standard method that subtracts the average of the high and low temperature from 65.

HDD1 = 65 - ((Daily High Temp + Daily Low Temp) / 2.0)

HDD2

Heating Degree Days (Experimental). This method subtracts the average of all 24 hours from 65.

HDD2 = 65 – Average Temp for the Day

GDD

Growing Degree Days - This is the standard method of taking the average high and low temperature and subtracting a reference temperature. For this product, it uses the common value of 50.

GDD = (Daily High Temp + Daily Low Temp) / 2.0 – 50