How much does it rain in Victoria?

Precipitation is another key aspect of Victoria's climate - and one that makes it quite unique among places along the B.C. coast - thanks to the rainshadow effect.  The east coast of Vancouver Island as well as the Gulf Islands, are in the rainshadow of the Vancouver Island mountains.  Moisture from the Pacific is dropped in abundant amounts on the west coast of Vancouver Island as the air lifts up over the mountains.  As the air flows back down to the east coast lowlands of Vancouver Island, it tends to warm and dry out, resulting in much less rain.  Victoria is unique because it is also in the rainshadow of the Olympic Mountains in Washington State.  The Olympics are higher than the mountains on Vancouver Island and the resulting rainshadow effect is stronger. Even though Victoria is on the edge of the Olympic rainshadow, this still results in much less rain than other areas of Vancouver Island or the Gulf Islands.  This is especially true around the southeast part of Greater Victoria (the City of Victoria, Oak Bay, and the southeast part of Saanich), which is most affected by the Olympic Mountain rainshadow.  Below is a radar image from February 22, 2014 of the southern Vancouver Island and western Washington.  You can clearly see the rainshadow,  which appears as a hole in the rain that includes Victoria as well as parts of Washington State (around Sequim and Whidbey Island).  This is a pretty typical location for the rainshadow.

Average annual precipitation at Victoria Gonzales is 641 mm for the 1981-2010 period.  Victoria Airport, 25 km to the north, receives 883 mm - nearly 40% more precipitation.  Even more astounding is the change in precipitation amounts as you head west from Victoria and out of the rainshadow.  Port Renfrew, located just 80 km west of Victoria on the exposed outer coast of the Island, receives an average of 3,671 mm of precipitation annually - nearly six times as much as Victoria.

Victoria receives less than half as much precipitation as Vancouver (1560 mm at Vancouver Harbour).  Victoria also receives less annual precipitation than all major cities in Canada east of the Prairies.  For example, Toronto averages 786 mm, while Montreal gets 1,000 mm and Halifax gets 1,396 mm.

Aside from the amount of precipitation Victoria receives, the other interesting thing is the seasonal pattern.  The Prairies receive the bulk of their precipitation during the summer, while winters are typically quite dry.  Most locations in Canada east of the Prairies receive roughly similar amounts of precipitation throughout the year.  B.C., especially along the South Coast, is quite unique in having a late fall/winter rainy season and a summer dry season, and this is most pronounced in Victoria.  Victoria Gonzales gets 119 mm of precipitation in November, its wettest month.  That's nearly ten times the average July rainfall total of 12.6 mm.  Victoria receives over half of its annual precipitation during just three months  - November, December, and January.  In contrast, it receives less than 8% of its annual precipitation during the three summer months (June to August).  In fact, Victoria is by far the driest major city in Canada during the summer.  It's 50 mm total average summer rainfall compares with 160 mm for Vancouver, 217 mm for Calgary, 225 mm for Toronto, 270 mm for Montreal, and 285 mm for Halifax.  Even desert-like  Osoyoos gets 84 mm of rain during the summer - nearly 70% more than Victoria.

Victoria gets 140 days annually with some measurable precipitation.  This varies from fewer than 5 days with measurable rain in both July and August, to nearly 19 days in November.

The wettest month on record at Victoria Gonzales is 337 mm in January 1935.  Although measurements weren't recorded for Gonzales, November 1990 was a very wet month in Victoria.  Nearby Victoria Phyllis Street received a record 395 mm that month.  For its driest month on record, Victoria has experienced calendar months with  no precipitation eight times: August 1901, July 1914, July 1922, July 1926, July 1958, August 1986, September 1991, and August 1998.  Victoria has had months with less than 1 mm of rainfall 23 times: once in May, twice in June, eleven times in July, eight times in August, and once in September.  The driest year at Victoria Gonzales was 1978, with 383 mm, while the wettest year on record was 1933 with 945 mm.  Again, although precipitation wasn't measured at Gonzales in 1990, the annual precipitation at nearby Victoria Phyllis Street was a record-breaking 1,084 mm.

The table below shows average monthly rainfall, snowfall, and total precipitation at Victoria Gonzales, as well as days with measurable precipitation.  Nearly 97% of the precipitation at Victoria Gonzales falls as rain.  We'll look at snowfall in more detail in the next post.