How do you dtermine degree days?
Degree day computations are fairly simple. To compute the number of degree days for any day,
you first must calculate the average temperature for that day. Then degree days are measured
from a baseline of 65 degrees. If the average temperature is warmer than 65 degrees, you have
COOLING degree days, and if the average is colder than 65 degrees, they are labelled as HEATING
degree days. An example:
If the average temperature for a day was 60 degrees, you subtract 60 from 65, and the result is
5 HEATING degree days. If the average temperature was 70 degrees, you subtract 65 from 70, and
the result is 5 COOLING degree days.
These numbers are useful to utility companies, such as the natural gas and electrical companies.
They can predict very accurately how much electricity or natural gas will be used, based on the
Here are a couple of links to pages that give a clear and detailed description of degree days,
how they are calculated, and how they are used.
Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO
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Update: June 2012