Weather & Climate
Degree days calculator.
Turn daily high and low temperatures into heating, cooling, or growing degree days, then multiply by a run of similar days.
Inputs
Degree-day total
Fill the form and press Calculate.
What degree days measure
The National Weather Service defines a day’s mean temperature as the high plus low divided by two. Heating degree days are the amount below the base; cooling degree days are the amount above it. Growing degree days use the same basic idea with a crop-specific base.
Source: NWS degree-day guidance. A custom base is intentional: 65°F / 18.3°C is common for building energy use, while crops and local practices use other thresholds. Official NOAA products can use more detailed daily observations than this midpoint estimate.
Planning estimate
Use your utility, agricultural extension, or official climate dataset’s published method when a contract, bill, crop model, or compliance decision depends on the total.