Wednesday, June 3, 2020

How rainy is Victoria compared with other cities in Canada? It depends on where in the region you are.

When talking about Victoria's climate, this blog primarily uses data from the Victoria Gonzales weather station.  This station, located in the southeast part of the City of Victoria near the border with Oak Bay, was Victoria's official weather station for many decades.

Thanks to its southeastern location, precipitation at Victoria Gonzales is strongly impacted by the Olympic Mountain rainshadow.  That influence tends to lessen the further north and west you go in the Greater Victoria region.  Thus, when we've stated on the blog that Victoria gets less rainfall than most cities in Canada, that is based on rainfall in Victoria Gonzales, and is not necessarily true for some of the wetter parts of the region.

Below is a chart that compares average annual precipitation at various locations in Greater Victoria with major cities across Canada.  As you can see, annual precipitation at both Victoria Gonzales (608 mm) and the University of Victoria (643 mm) is relatively low.  Across Canada, only cities in the B.C. Interior and on the Prairies are drier.  In fact, just 18% of Canada's urban population lives in cities with lower annual precipitation than these two locations.   Esquimalt Harbour (861 mm) and the Victoria Airport in North Saanich (883 mm), fall more in the middle of the pack among Canadian cities, with roughly half of Canada's urban population living in cities that are drier than these locations.  Meanwhile, Langford (1133 mm) and Sooke (1236 mm) get more annual precipitation than most cities in Canada: only cities in southwestern B.C., parts of Quebec, and Atlantic Canada get more precipitation.  In fact, 81-86% of Canada's urban population lives in cities that are drier than these locations.


Monday, June 1, 2020

Spring 2020: close to average temperatures, but slightly drier than normal

Meteorological spring consists of March, April, and May.  Spring 2020 in Victoria brought average overall temperatures and slightly less rainfall than normal.  The spring started out cooler than normal in March and ended with a warmer than normal May.  Typically, Victoria sees successively drier weather as spring progresses, but this year precipitation was fairly evenly distributed throughout the three spring months, meaning that March was significantly drier than normal, while May was slightly wetter than normal.

The mean temperature this past spring at Victoria Gonzales was 10.0 degrees (ave. high 13.4 & ave. low 6.6), which is right on the 30-year average.  Spring began with a cold March, which was 1.3 degrees cooler than normal.   April experienced normal temperatures overall, while May was 1.1 degrees warmer than normal.      

The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales during spring 2020, compared with the 30-year averages.  You can see that temperatures in March were generally below average, with a short cold spell in the middle of the month.  The first 5-6 days of April were cooler then normal, but the rest of the month was generally slightly warmer than normal.  May featured two short "heat waves" on May 8-10 and on May 27-29, which pushed the average temperature for the month to above normal, despite most of the rest of May being slightly cooler than normal.  


Spring 2020 saw  two days when the overnight low fell below freezing: March 14 and 15.  On average, Victoria sees just 0.6 days each spring with a low temperature below 0.  The coldest temperature of the spring was March 14 when the temperature dropped to -0.7 degrees.  The warmest day of the spring was 27.8 degrees on May 10.  Spring 2020 in Victoria saw three days with temperatures above 25 degrees, much more than the average of just 0.5 25-degree plus days each spring.


Daily Max & Min Temperatures in Victoria, Spring 2020




Victoria received 82 mm of precipitation during the March to May period.  That's about 74% of the 30-year average spring precipitation of 112 mm, making it the 24th driest spring at Victoria Gonzales in 107 years - in other words, drier than normal, but not exceedingly dry.  March saw 28 mm of rain - just 57% of normal, April saw 25 mm of rain -  76% of normal, and May was right on the normal rainfall of 29 mm.  

Spring 2020 also saw fewer than average days with measurable rainfall: just 28 days compared with the average of 33.6.  There were 13 days in March, 7 days in April, and 8 days in May with measurable rainfall.  The longest dry spell was 17 days, from April 5-21.  


The chart below shows daily precipitation during spring 2020, and compares the cumulative precipitation with the 30-year average.   Cumulative rainfall dropped below the average early in the spring, and stayed below average throughout.  April 22, with 14.6 mm, was by far the wettest day of the spring, which was more than double the second wettest day: 6.6 mm on March 30.



Daily & Cumulative Rainfall in Victoria, Spring 2020


The chart below compares the precipitation amounts in Victoria this spring with other locations in the region.  As is typically the case, Victoria Gonzales had the lowest amount, with a total of 82 mm.  However, as with this past winter, the difference in precipitation levels between Victoria and other locations was less than usual.  That's because while spring rainfall was 74% of normal at Victoria Gonzales, it was just 63% of normal at Victoria Airport and just 43% of normal in Vancouver.  Looking at this another, Vancouver typically gets more than 3 times as much rain in the spring as Victoria does, but in 2020 it received less than double Victoria's rainfall.  On the other hand, rainfall in Seattle was actually above normal this spring, so while it normally gets just under double Victoria's spring rainfall, this year it received nearly triple, with 237 mm.    

Regional Comparison of Precipitation, Spring 2020