Degree Day Information

  • Snowy birdhouseReflects how warm or cold it was during a specific period.
  • The larger the number, the colder the temperature was.
  • You usually use more heating fuel in colder weather because your furnace is working harder to maintain comfortable temperatures.
  • Degree day calculations are based on the assumption that a building does not require any heat if the outside temperature averages 65 degrees during a 24-hour period.

Calculate degree days

  1. Add the highest temperature to the lowest temperature for the period.
  2. Divide the total by two.
  3. Subtract the result from 65.


If the day's high temperature was 30 degrees and the low was 10 degrees:

Use degree days to compare energy consumption for a given time period:

  • Calculating your energy use per degree day will reduce the weather impact on your comparison.
  • To find natural gas use per degree day, divide the number of therms used by the number of degree days for the same period.

Example therms for an example home:

  • 137 therms for the billing period in December 2019.
  • 143 therms for the billing period in December 2020.

Degree days for example billing period:

  • 1,080 degree days during the December 2019 billing period.
  • 1,324 degree days during the December 2020 billing period.

Natural gas use per degree day:

  • .127 in December 2019.
  • .108 in December 2020.

This home was using energy more efficiently in December 2020.

Related links

Find heating and cooling degree days and temperature information at:

Wisconsin State Climatology Office