Growing Degree Days

There have been a couple of articles in the Fairbanks Daily News-Miner of late about what a great growing season summer 2010 has been. Yet neither seasonal temperatures nor precipitation have seemed outstanding. One explanation may be that the summer has been unusually balanced. Rather than six weeks of very warm weather, temperatures have been mild over a long period. This is reflected in the plots above, based on data from Keystone Ridge. The plot on the left shows Growing Degree Days (daily mean temperatures above 50F) May through August, with individual months noted. Like the raw temperature plot, the 2010 total is above the 15 year mean, but not by a lot, and several summers were higher. However, the plot on the right tells a different story. Here, the monthly percentage of total Growing Degree Days is plotted. 2010 has the most even distribution across the four months of any summer.* The contrast with last year, which had almost the same total number of GDD, is remarkable. In 2009, almost half the seasonal GDD are crammed into July.

*The remaining six days in August 2010 will add only a small number of GDD to the total and will slightly increase the balance in the GDD distribution for this year.