This Winter Is 37% Warmer than 2010-11 (by Heating Degree Days)
Last week was Groundhog Day, and my question that day was, How can Punxatawney Phil (the weather predicting groundhog) or General Beauregard (his Southern counterpart) say anything at all about more winter when we haven't really had a winter at all? Yes, it's been quite warm this winter, especially in comparison to last year. So I thought I'd check to see just how much warmer it's been.
First of all, looking at the number of Heating Degree Days (HDD) is a great way to compare the cold weather of one year to another. There are three nice websites I'm aware of where you can get the Heating Degree Days for your location:
You should definitely check them out.
Heating Degree Days are a way of looking at how much time your area has spent below a given temperature, called the baseline temperature. The most commonly used baseline here in the States is 65° F, so here's how it works:
- 1 minute at 64° F gets you 1 Heating Degree Minute.
- 1 hour at 60° F would be 5 Heating Degree Hours.
- 24 hours at 30° F accumulates 35 Heating Degree Days.
See how it works?
One way that you can use these numbers is to calculate the amount of heating your home needs. Since your heating load depends on how cold it is outside, the more Heating Degree Days you have, the more heating you have to pay for. The basic equation for this is:
The number of Heating Degree Days tells you the ΔT over a given time period.
So, here in Atlanta, we had a total of 3396 HDD in the 2010-11 winter. It was really cold last year, and we actually had snow three times. We normally get one little snow a year, but we even got shut down for a whole week with snow that turned to ice on the roads and then stuck around. Our 30 year average is about 3000 HDD, so last year was colder than normal.
This year however, if we look just at December and January, we find a huge difference:
December 2010: 891
January 2011: 823
January 2012: 570
The 37% number in the title of this article comes from comparing the HDD of just those two months. We had 1714 HDD in those months in 2010-11 and 1076 HDD this winter. It's great for heating bills and getting outside and doing stuff here. Not so great killing bugs though.
How do your Heating Degree Days this winter compare to last winter?
Photo by AlicePopkorn2 from flickr.com, used under a Creative Commons license.