Degree days without the mystique
A cold April is not a moral failing. Degree days are a way to say how much heating the weather asked for, in the postcode you actually occupy.
When gas use rises, someone will claim the occupants “left the windows open.” Sometimes they did. Often the weather simply asked more of the boiler. Degree days are a published count of how far outdoor temperature sat below a base, summed across the month.
We use figures that match the region of the site, not a single national average. A mill conversion in Austonley does not share a climate with a coastal depot. If we cannot obtain a nearby series, we say so and leave the weather note qualitative.
Degree days help with heating fuels. They do not excuse a summer electricity spike from server rooms or a kitchen that added a second shift. We keep those comments in different paragraphs so a reader is not invited to blame the frost for a freezer.
Base temperatures differ between offices and warehouses. We record the base we used. Changing it later to make a chart look flatter is not a service we offer.
If your previous pack ignored weather entirely, a first weather-adjusted year can look like a sudden improvement or a sudden failure. It is usually neither; it is the first time the fence and the frost were named together.