Monthly Archives: September 2017

Thaw-degree days in Fairbanks

For a garden club presentation I gave this past spring, I graphed the weather records from the Fairbanks Experiment Farm to look at changes over time. The biggest one goes back to 1948 and is for thaw degree days. This chart is a broad indicator of the warmth of the season. Average daily air temperature records are subtracted from a baseline temp of 32F. This assumes that plant growth occurs at any temp above 32F but not below. This is not quite accurate because cell sap does not freeze at exactly 32F, and there are Alaska native plants that can grow at temps that are a few degrees below 32F. On the other end of the spectrum, garden plants have all kinds of lower limits to growth- cool season crops are often around 40 – 45F below which growth stops. Warm season crops are more like 50F and above. However, choosing 32F at least allows a comparison of the seasons. The thaw degree- day (TDD) chart is split into three just to fit it onto a page. Check out the differences among years and the mean TDD on each chart. The timeline is waaaay too short to make conclusions on climate change, but it is interesting to see the incredible variation from year to year.      1948 – 2016 Thaw degree days