A heating degree day (HDD) or cooling degree day (CDD) is an index used to determine the amount of energy needed to heat or cool a building. The number of heating or cooling degrees in a day is defined as the difference between a base temperature – 65° Fahrenheit – and the outside temperature. If, for example, the temperature outside is 55° F, then we would say it is a ten-degree day. Organizations, such as the State of Iowa, use this information to estimate seasonal heating and cooling demands.
| Jan | Feb | Mar | Apr | May | June | July | Aug | Sept | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| HDD | 1469 | 1151 | 904 | 501 | 222 | 44 | 10 | 31 | 136 | 462 | 881 | 1320 |
| CDD | 0 | 0 | 1 | 3 | 66 | 180 | 275 | 218 | 67 | 10 | 0 | 0 |