Heating Degree Days
How often do residents require home heating?
Heating Degree Days (HDDs) measure how many days in a year the outdoor temperature falls below a base threshold—typically 65°F—indicating when residents are likely to need heating. HDDs are used to estimate energy demand and signal how climate and housing systems affect the cost and comfort of indoor living.
When HDDs are high, it means colder weather is driving up heating needs, which can put significant financial strain on low-income households living in poorly insulated homes. Climate change adds complexity, as some regions may experience fewer cold days overall but face more extreme cold snaps. Cities can respond by investing in energy efficiency, weatherization programs, and utility assistance to help residents stay safe and warm.
When HDDs are lower, it can reflect milder winters and decreased energy demand, reducing heating costs for residents. This can signal positive environmental trends and improved comfort—particularly when paired with resilient housing and efficient energy systems.
Primary Indicator
Total number of accumulated days that require heating (below 65°F) during the year in the city
Data were obtained from Oregon State University's PRISM Climate Group. The total number of heating degree days (HDDs) is calculated by subtracting 65 minus the mean daily temperature for days when the daily average temperature is under 65 degrees Fahrenheit, then summing the values for every month and adding each month to get the annual total between July and June of the following year. Data is obtained directly from the source and measured in Fahrenheit/days. For more information on the methodology and calculations, please visit the source's site here.