Volume 6 Issue 2
Chris Benedict
WSU Whatcom County Extension
NOTE: This article was originally written about two weeks ago prior to the snowstorm that was described as #snowapocoplaypse or #snowmaggodon on Twitter. I am told that much snow was an anomaly (there are not good snow accumulation records for Whatcom County), but the below article also shows that we have had one of the colder winters in recent years…so far.
I’ve heard many people talk about how cold it’s been this winter. While winter is technically another 40 or so days I wanted to look back over the past nine winters (focused on the months of 9/1 through 2/1 – Yes I know that is not technically winter) to see if ’16-’17 stood out thus far.
All data reported here comes from WSU’s AgWeatherNet stations throughout Whatcom County (we are lucky to have four). In the case where averages across years were reported, these values were calculated by taking the average value (e.g. daily max temperature) across years on the same date.
Daily Maximum, Mean, and Minimum Temperatures (9/1 – 2/1)
Figure 1 shows a combination of several data points including the daily maximum, mean, and minimum temperatures. Each 24-hour period has one value for these different categories and the values for 2008-2016 (calculated as described above) are shown as columns colored grey (max), blue (mean), or orange (min). The bright red trend line is based on the minimum daily temperature (averaged across the ’08 – ’16 time period). The maximum (purple), mean (yellow), and minimum (green) temperature lines represent daily values for the ’16 – ’17 time period. Several things to point out include:
• Up until early December, our fall minimum temperatures were largely above normal.
• Within the first week of December we entered into an abnormally cold period where even our maximum daily temperatures did not reach above the eight year mean for daily low temperatures.
• For the months of December and January 58% of the days had lows below the average minimum for the prior eight-years.
• Early to mid-January (when we had several clear cool days) exhibited some of the lowest daily lows recorded during this time period.
Figure 1. Maximum, Mean, and Minimum Daily Air Temperature Whatcom County, WA 9/1 through 2/1 (source)
Figure 2. Number of Days (9/1/ – 2/1) below 32ºF, Whatcom County, WA (source)
So what does all this mean especially for the roughly 18,000 acres of perennial horticultural crops in Whatcom County? While ’16 – ’17 looks abnormally cold, so far it’s not completely out of the ordinary. The combination of low temperatures with wind though may impact exposed fields. On a positive note, ongoing cold hardiness research by Lisa DeVetter and Gwen Hoeheisel has found that we have not reached injurious temperatures in ‘Duke’ or ‘Draper’ in western Washington for the winter of 2016-2017 thus far.