Sunday, March 5, 2017

Victoria's cold winter of 2016-17

We've recently come to the end of meteorological winter (December 1 to February 28), and it was definitely an unusual winter in Victoria.  The biggest stand out was the temperature - this past winter was the coldest in 38 years in Victoria.  The last time we had a winter this cold was back in 1978-79.  Victoria has actually experienced 20 winters in the last 120 years that were at least this cold.  However, all of those winters were prior to 1980, so we're just not used to it  any more!

The mean temperature this past winter was 3.9 degrees, roughly 2 degrees below the 30-year average of 5.8 degrees.  The average daily maximum/minimum this winter was 6.1/1.6, again roughly 2 degrees below the normal winter daily max/min of 7.9/3.6. 

The chart below compares the daily maximum and minimum temperatures this winter with the 30-year average temperatures.  You can see that the temperatures were pretty consistently below average, with just a couple of brief spells of milder weather. 

Daily maximum & minimum temperatures in Victoria, winter 2016-17


Victoria experienced 25 days when the temperature dropped below freezing this winter, compared with the average of 8.8 days.  Again, that’s the most days since the winter of 1978/79.  However, the record was 41 days in 1912/13.  While we had a lot of overnight lows below freezing, it never really got that cold in Victoria this winter.  The coldest temperature was -3.8 degrees on December 17.

Conversely, Victoria experienced daytime temperatures above 10 degrees on just 7 days this winter, compared with the average of 20 days.  Last winter (2015/16) there were 28 days above 10 degrees and the winter before that (2014/15) there were 42 such days - six times as many as this winter.  To put it another way, just 8% of winter days this year were above 10 degrees, compared with 47% of winter days in 2014/15.   

The colder weather was partly the result of a number of arctic outbreaks, bringing cold sunny weather to Victoria.  As a result, total precipitation for the winter was below normal: 222 mm versus the 30-year average of 264 mm.  The chart below compares the daily and cumulative precipitation at Victoria Gonzales this past winter with the 30-year normal precipitation.  While December was a bit wetter than normal, January was very dry and February was about average.  The highest daily rainfall was 26 mm on February 9.  Overall, there were 46 days with measurable precipitation this winter, which was right on the average.

Daily & cumulative precipitation in Victoria, winter 2016-17


As usual, Victoria was much drier than surrounding areas, as shown in the chart below.  Compared with Victoria Gonzales (222 mm), the Victoria Airport (315 mm) had 50% more precipitation, while Seattle (430 mm) and Vancouver (469 mm) both had about twice as much. 



Winter 2016/17 brought the first significant snowfall in 5 years to Victoria.  Not surprisingly, snowfall was above normal.  Total snowfall for the winter was 29 cm, almost double the 30-year average of 16 cm for December to February (total annual snowfall averages 20 cm in Victoria).  There was 8 cm of snow in December, just 1 cm of snow in January, and a whopping 20 cm in February (versus normal of 9 cm for December, 3.4 cm for January, and 3.6 cm for February). In terms of days with snow on the ground, Victoria got off not too badly (especially compared with Vancouver and up-Island): there were 5 days with at least 1 cm of snow on the ground this winter compared with the normal of 4.5 days during December to February.