The following article is retained for historical reference. Please use the Timeline Weather API to access degree day values.
Degree Days are a way to help determine how much warmth or cold there has been, typically over a season such as winter, summer or a plant’s growing season. Degree Days are used to determine a building’s typical heating or cooling requirements over a season. They are used in agriculture, farming and gardening to plan plant and crop planting, management and harvest dates.
We have recently enhanced the Timeline Weather API to include degree day support. You can now easily add degree day values to any weather query simply by adding a couple of extra parameters. For example, if you need the degree days for the past 30 days in CSV format, you can simple place this into your browser:
https://weather.visualcrossing.com/VisualCrossingWebServices/rest/services/timeline/London,UK/last30days?unitGroup=us&key=YOUR_API_KEY&include=days&elements=datetime,tempmax,tempmin,degreedays,accdegreedays°reeDayTempMaxThreshold=86°reeDayTempBase=50&contentType=csv
To learn more about how to download degree days in the Timeline Weather API, header over to the Timeline Weather API documentation.