Monthly heating degree days in Switzerland (weighted)

The heating degree days are the sum of the daily deviations of the average outside temperature of a room temperature of 20 °C, on those days when the average outside temperature is 12 °C or less. It is based on the experience that on average from an outside temperature of 12 °C must be heated in order to maintain a room temperature of 20 °C. The heating grade days are calculated for the whole of Switzerland by weighting measured values of 53 meteorological stations with the residential population living in their respective area. Since 2000, the weighting has been carried out according to the 2000 census.