The mean for annual heating degree days has dropped about 63 HDD from 1904-1963 at 6726 shown, to 6663 for 1963-2023, or 0.94%.
In the last 23 years, just 5 have been at or above the old mean shown, while 18 have been below. In the previous 23 years the pattern was much more even: 13 above the old mean shown and 10 below.
This is clearly a picture of recent moderating winters, but people forget that this comes on the heels of a prolonged period of much more severe winter cold extending 55 years from 1943-1997. During that period there were 40 winters above the old mean shown, and just 15 below it.
That cold period itself followed upon a previous period of previously well known warming where about 58% of the seasons in the record saw heating demand well below the old mean.
The Dust Bowl era. Maybe you've heard of it.
Higher mean heating degree day totals in the second half of the 20th century indicate its colder conditions compared with the eras book-ending it:
1904-1943: 6685 (40yrs)
1943-1997: 6883 (55yrs)
1997-2023: 6351 (27yrs).
