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

Sunday, April 19, 2020

Winter 2019-20: fairly normal temperatures but much wetter than normal

Meteorological winter consists of December, January, and February.  Overall, this past winter was slightly milder and much wetter than normal.  The mildness of this winter was entirely due to December, which was much warmer than normal, while February was slightly cooler than normal.  In terms of precipitation, December was slightly wetter than normal, but January, and to a lesser degree February, were much wetter than normal.

The mean temperature this past winter at Victoria Gonzales was 6.0 degrees, compared with the 30-year average of 5.8 degrees.  Winter began with a mild December, which was 1.1 degrees above normal.   January experienced normal temperatures overall, while February was 0.4 degrees cooler than normal.      

The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales during winter 2019-20, compared with the 30-year averages.  You can see that temperatures in December were generally above average.  January started out mild, experienced a short but sharp cold spell in the middle of the month, then returned to above normal temperatures towards the end of the month.  In February, temperatures were generally below average, especially at the beginning of the month.  The mildest day of the winter was 13.5 degrees on January 31.  The coldest day of the winter was January 14, when the temperature dipped to -5.7 degrees overnight, and the high temperature was only -2.0.  There was one stretch of 6 days from January 12-17 when the overnight temperature dipped below freezing, but there were no other days during the winter with below freezing temperatures.  On average, Victoria Gonzales gets 7.6 days with below freezing temperatures during meteorological winter.



Daily vs. average Max & Min temperatures, winter 2019-20 in Victoria




Victoria received 419 mm of precipitation during the December to February period.  That's nearly 60% more than the 30-year average winter precipitation of 264 mm, making it the 10th wettest winter on record at Victoria Gonzales (with 107 years of record-keeping), and the wettest winter in more than 20 years.  Precipitation was slightly above average in December (112 mm versus the normal 96 mm), but nearly double the normal in January (204 mm versus 107 mm) and 67% above normal in February (102 mm versus 61 mm).  

There were 55 days with measurable precipitation this winter, with 16 days in December, 25 days in January, and 14 days in February.  That's above the normal of 45 days with measurable precipitation that Victoria typically sees during the winter.  Victoria also saw a lot of really wet days this winter: it experienced 5 days with more than 25 mm of precipitation, versus the normal average of 1.6 such days.  There have only been 5 winters in 107 years at Victoria Gonzales with 5 or more days with 25 mm of precipitation.


The chart below shows daily precipitation during winter 2019-20, and compares the cumulative precipitation with the 30-year average.   Precipitation levels were generally close to the average during December, but quickly surged ahead of normal during January.  The wettest day of the winter was February 1st, with 33.8 mm of rain.  Four other days had more than 25 mm: 29.4 mm on December 20, 30.6 mm on December 31, 27 mm on January 6, and 28 mm on January 31.



Daily & cumulative precipitation, winter 2019-20 in Victoria


The chart below compares the precipitation amounts in Victoria this winter with other locations in the region.  As is typically the case, Victoria Gonzales had the lowest amount, with a total of 419 mm.  However, the difference in precipitation levels between Victoria and other locations was less than usual.  That's because winter precipitation was nearly 60% higher than normal at Victoria Gonzales, but only 17% above normal at Vancouver Airport, 37% above normal at Victoria Airport, and 47% above normal at Seattle.  

2019-20 Winter precipitation in Victoria and nearby locations

Victoria received 22 cm of snow during winter 2019-20, higher than the average winter snowfall of 16 cm.  (Victoria averages 20 cm of snow annually, but some of that falls during November and March, which are not part of meteorological winter).  All of this winter's snowfall was during 4 days in mid-January, which was much snowier than the average January snow total of 3.4 cm.  There was 5 days this winter with snow on the ground in Victoria, very close to the average of 4.8 days each winter with snow on the ground.

Thursday, January 2, 2020

Review of Victoria's Weather in 2019

Victoria was drier and close to normal temperatures in 2019.

The mean temperature at Victoria Gonzales for 2019 was 10.7 degrees C, just very slightly above the 30-year average of 10.6 degrees.

In terms of average temperature, February was the most unusual month of 2019, being more than 4 degrees below normal.  It was the second coldest February on record at Victoria Gonzales, and the coldest since 1936.  October was also a cold month, being 1.2 degrees below the average, and the coldest October since 1984.  On the other other hand, January, May, and December were all more than a full degree warmer than normal in 2019.

The warmest temperature of 2019 came quite early, on June 12.  It was the only day in 2019 to hit 30 degrees or higher.  There were just 6 days in 2019 with daily maximums above 25 degrees, compared with the average of 9 days.  The coldest temperature in 2019 was -5.6 degrees on February 4.  That was the coldest temperature recorded at Victoria Gonzales in more than 5 years.  There were 18 days in 2019 when the temperature went below 0, nearly double the long-term average of 9.5 days.  February accounted for 13 of the 18 days with frost in 2019.

The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales in 2019, compared with the long-term normal temperatures.  You can clearly see the cold snap which covered most of February, but was especially pronounced during the first part of the month.  You can also see the occasional warm spikes, such as 21 degrees in March, 25 degrees in early May, and 30 degrees in mid-June.  There were also some notable cold spikes in October and late November.



Daily Max & Min Temperatures at Victoria Gonzales, 2019

2019 was drier than average in Victoria.  There was 567 mm of precipitation, 87% of the normal 654 mm.  November and March were particularly dry in 2019, with both months receiving less than half of their normal rainfall.  July through September was wetter than normal in 2019, although with this being a dry time of year, it wasn't really that wet.

Thanks to its location in the Olympic Mountain rain shadow, Victoria receives less precipitation than surrounding locations, and 2019 was no exception.   The chart below compares annual precipitation in 2019 in locations around Victoria.  The Victoria Airport recorded 706 mm, 25% more than than Victoria Gonzales.  Vancouver Harbour recorded 1140 mm in 2019, while Seattle Airport received 861 mm.  While Vancouver received about twice as much precipitation as Victoria in 2019, that's actually less than the long term average, which sees Vancouver getting about 2.4 times as much precipitation as Victoria.

Annual Precipitation in Victoria and the Surrounding Region, 2019
The chart below shows daily and cumulative precipitation at Victoria Gonzales in 2019.  You can see that the cumulative precipitation in 2019 (red line) stayed below the average (blue line) for most of the year.  .

Daily & Cumulative Precipitation at Victoria Gonzales, 2019

There were just 111 days with measurable precipitation in 2019, well below the normal of 131 days.  In fact, that was the lowest number since 1987, when there were 105 precipitation days.  The wettest day in 2018 was January 3, with 36 mm.  Despite being a drier than average year, there were 4 days with more than 25 mm of rain in 2019, one more than the long term average 3 days per year.  There were 15 days with at least 10 mm of rain, close to the  normal of 16 days.

Victoria had more snow than normal in 2019, all of it from a snowy period in February.  Victoria received 26 cm of snow in 2019 compared with the long term average of 20 cm.  As mentioned, all of this snow fell in February, when Victoria typically receives less than 4 cm of snow on average.  There were 7 days with measurable snowfall in 2019, again all in February.  This was the most days with snowfall since 2008, and nearly double the normal of 8 days per year.  There was snow on the ground for 7 days in 2019, compared with the long term average of 4.8 days.  2019 saw the most days with snow on the ground in Victoria since 2008.

Wednesday, December 18, 2019

What are the chances of a White Christmas in Victoria?

It's just one week until Christmas, so the long range forecast is accurate enough to know that the chances for a White Christmas this year in Victoria are virtually nil.  The photo below was taken on the last White Christmas in Victoria, not long ago in 2017.  It won't look like that this year.



So what is the historical likelihood of having a White Christmas in Victoria?  Environment Canada defines a White Christmas as having 2 cm or more of snow on the ground on Christmas morning.  Using that definition, there have been just 6 White Christmases in Victoria since 1914 when the Victoria Gonzales weather station opened: 1937, 1971, 1990, 1996, 2008, and 2017.  So 6 out of the last 106 years have seen snow on the ground on Christmas morning, meaning that over that period there has been a 5.7% chance of having a White Christmas.

Interestingly, the frequency of White Christmases in Victoria has actually increased in recent years.  Prior to 1990, there were just 2 White Christmases in the 76 years from 1914 to 1989 - that's just a 2.6% chance.  But in the last 30 years (1990-2019), there have been 4 White Christmases, resulting in a 13.3% chance.  Amazingly, White Christmases have been have been more than 5 times as frequent in Victoria over the past 30 years than they were in the previous 76 years!  What's even more surprising, is that this has happened as the overall amount of snowfall in Victoria has decreased: from 1914 to 1989 average annual snowfall at Victoria Gonzales was 29.9 cm, while from 1990-2019 the average annual snowfall in Victoria was just 16.4 cm.  So why has the frequency of White Christmases increased?  It's really just up to random chance - the very infrequent snowfalls that we get in Victoria have just happened to occur at or just before December 25, giving us White Christmases.  2017 was a good example of that fortuitous timing of Christmas snow: it snowed overnight on Christmas Eve, providing a White Christmas, but it was melting by evening and all gone by Boxing Day.

Victoria averages 4.7 days per year with 2 cm or more of snow on the ground.  On any given day between November 1 and March 31, there is a 3.1% chance of having snow on the ground.  This likelihood peaks during the last 10 days of December and the first 10 days of January, as shown in the chart below.  During that 20-day period, which includes Christmas, the chance of having snow on the ground ranges between 6% and 9%.

Average Frequency of Snow on the Ground in Victoria (1955-2019)














How does Victoria compare with other locations Canada?  The chart below compares the of having a White Christmas for several cities across Canada.  To make the comparison, I have used the 1955-2019 period, for which data is readily available for a number of locations.  In Victoria, there were 5 White Christmases during this 65-year period, resulting in a 7.7% chance.  Vancouver had 6 White Christmases during this period, or a 9.2% frequency.  As shown in the chart, other Canadian cities have significantly higher chances of a White Christmas: in Toronto it's 47%, while Calgary and Halifax have a 56-58% chance.  White Christmases are almost assured in most other major Canadian cities, ranging from 75% in Montreal to 98% in Winnipeg.

Chance of a White Christmas for Selected Canadian Cities
Given that Vancouver averages 8.6 days per year with at least 2 cm of snow on the ground versus 4.7 days for Victoria, it's surprising that the chance of a White Christmas isn't much greater in Vancouver.  Again, this seems to come down to random chance.  While Vancouver only had one more White Christmas during the 1955-2019 period compared with Victoria, those White Christmases have been much snowier in Vancouver.  For Victoria's 5 White Christmases, the average snow depth was 7 cm, while for Vancouver's 6 White Christmases, the average snow depth was 20 cm.

So if White Christmases are pretty rare in Victoria, what does the weather typically look like on Christmas Day?  Based on the 30-year "normals", the average high temperature is 6.8 C while the average low is 3.1 C.  The daytime high on Christmas Day in Victoria is between 5 C and 10 C 67% of the time; it's between 0 C and 5 C 23% of the time and between 10 C and 15 C 10% of the time.

On average, Victoria gets 2.6 mm of rain on Christmas Day, although there has only been measurable rain on 51% of Christmases.  The wettest Christmas Day was 1972, with 51 mm of rainfall.  Meanwhile, Victoria averages 2.4 hours of sunshine on Christmas Day, or about 30% of the 8 hours that is possible on December 25.  There has been at least some measurable sunshine on Christmas 63% of the time, so Victoria is more likely to get at least some sunshine on Christmas Day than to get some measurable rain.



Tuesday, December 3, 2019

Fall 2019 in Victoria: Cooler and Drier than Normal

We're now at the end of meteorological autumn, which runs from September 1 to November 30.  Overall, fall 2019 was slightly cooler and drier than normal.  September was close to normal temperatures while October was the coolest in 35 years.  November was slightly warmer than normal.  Normally in the fall, rainfall amounts  in Victoria increase sharply as the season progresses - November averages more than 5 times as much rain as September.  However, this fall, rainfall was much more evenly distributed throughout the season than is normally the case.

Victoria received 190 mm of rain this fall, 84% of the 30-year average of 226 mm.  Victoria received more than double its normal rainfall in September, close to normal rainfall in October, then only 52% of normal rainfall in November.   The 68 mm of rain recorded this November was tied for the 7th driest in the past 30 years, so while it was  drier than normal, it was nowhere near record-setting (just 15 mm in November 1979).


There were 36 days with measurable rainfall during fall 2019, close to the normal 37 days.  The biggest anomaly was  in November when there were just 10 days with measurable rainfall compared with the normal 18 days.  There was a 14-day dry streak from October 26 to November 8 - the longest such streak on record during the month of November at Victoria Gonzales.  Once you get into November, dry streaks are pretty rare in Victoria.  By contrast, the longest October dry streak was much longer at 33 days, ending October 28, 1987.

The chart below shows daily precipitation during fall 2019, and compares the cumulative precipitation with the 30-year average.   Cumulative precipitation was above average for most of the fall, thanks to the wet start in September and early October.  This was followed by the 14-day dry stretch noted above during late October and early November.  Some rain did return in mid-November, but not enough to bring seasonal rainfall to normal levels.  The wettest day of the fall was November 17, with 30 mm, accounting for nearly half of rainfall during the entire month of November.


Daily & Cumulative Rainfall in Victoria, Fall 2019

Victoria is usually much drier than surrounding locations in the region, but that was less case this fall.  The Victoria Airport in North Saanich normally receives about 20% more rain during the fall than Victoria proper, but this year the Airport received only 4% more (197 mm at the Airport vs. 190 mm at Victoria Gonzales).  Seattle normally receives about 30% more fall rainfall than Victoria, but this year it only got about 16% more rain.  On the other hand, Vancouver received 419 mm, or more than twice as much rain as Victoria, which is fairly typical.

Comparison of Rainfall in the Victoria Region, Fall 2019

The mean temperature this past fall at Victoria Gonzales was 10.7 degrees, cooler than the 30-year average of 11.0 degrees.  This was the first cooler than average fall since 2013 - the last five falls have averaged 11.7 degrees.  For the fall as a whole, the average daily maximum was 13.5 degrees (0.5 degrees cooler than the long-term average) while the average daily minimum was 7.9 degrees (just 0.1 degrees cooler than the long-term average).        

The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales during fall 2019, compared with the 30-year averages.  Generally, daily max temperatures were slightly below the average for most of the season, except for a brief heatwave in early September and a warmer than average period in mid-November.  Daily minimum temperatures fluctuated on either side of the average.  The warmest temperature of the fall was 25.1 degrees on September 5.  The coldest temperature of the fall was a chilly -0.8 degrees on November 30, the last day of the season.  There were 2 days this fall (November 29 and 30) when the minimum temperature went below freezing.  The average first frost at Victoria Gonzales is December 26, so frost in November is earlier than normal.


Daily Max & Min Temperatures in Victoria, Fall 2019

Wednesday, September 4, 2019

Summer 2019 in Victoria was statistically normal overall

Meteorological summer runs from June 1 to August 31.  Overall, this summer saw close to normal rainfall and temperatures - it was just very slightly drier and a bit warmer than normal.   However, while June was drier than normal, July and August were both a bit wetter than normal and we experienced about twice as many days with significant rainfall in July and August than we normally do.

Victoria received 48 mm of rain this summer, close to the 30-year average of 52 mm.  Looking at the past 106 summers in Victoria (going back to 1914, when the Gonzales Observatory opened), this past summer ranked as the 52nd wettest – so pretty much in the middle of the pack.  However, this doesn’t mean that rainfall was consistently average throughout the summer.  Victoria received about half of its normal rainfall in June, but then received 33% above normal rainfall in July and 9% above normal rainfall in August.    

While the overall amount of rain was fairly typical this summer, the number of days with significant rainfall was higher than normal.  There were 12 days with more than 1 mm of rainfall this summer, compared with the normal 9.7 days.  Furthermore, 11 of these days were during July and August – the driest part of the summer, which normally sees just 5.3 days with 1 mm or more of rain.  That is likely why this summer seemed a bit more unsettled than the usual in Victoria.  

Another way to look at this is drought periods, or consecutive days without measurable rainfall.  Looking back at summers since 1914, on average there has been a 29-day stretch without measurable rainfall in Victoria.  However, this year the longest stretch was just 19 days – June 8-26.  

The chart below shows daily precipitation during summer 2019, and compares the cumulative precipitation with the 30-year average.   Cumulative precipitation was below average for most of June, but then caught up to normal following a wetter period in late June and early July.  Cumulative rainfall stayed just below normal for the rest of the summer.  The wettest day of the summer was June 27, with 8.4 mm.  Two other days had more than 5 mm – July 2 and August 2.


Daily & Cumulative Rainfall in Victoria, Summer 2019

Compared with 48 mm of rain at Victoria Gonzales during June to August, U-Vic (45 mm) and Esquimalt Harbour (52 mm) had similar amounts, while the Victoria Airport  was wetter, with 72 mm.  The chart below compares the precipitation amounts in Victoria this summer with other locations in the region and across Canada.  Vancouver and Seattle both received about 90 mm of rain.  That was close to normal for Seattle, but well below normal for Vancouver.  Typically, Vancouver receives about 3 times as much rain in the summer as Victoria, but this year it only received about twice as much.  As is typically the case, other major cities in Canada were much wetter than Victoria – generally receiving four to seven times as much rain.  


Total Rainfall Comparison, Summer 2019
The mean temperature this past summer at Victoria Gonzales was 16.0 degrees, warmer than the 30-year average of 15.6 degrees but well below the record warm summer of 2016 when it was 16.9 degrees.  The past six summers have been warmer than average in Victoria.  While June and August were warmer than normal this summer, July was right on the average.  For the summer as a whole, the average daily maximum was 20.0 degrees (just 0.2 degrees above the long-term average) while the average daily minimum was 12.0 degrees (0.7 degrees above the long-term average).   Around the region, the daily average maximum was cooler at Victoria Harbour (18.9 degrees), but warmer at U-Vic (22.2 degrees).     

The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales during summer 2019, compared with the 30-year averages.  Generally, temperatures stayed fairly close to the long-term averages.  The most significant exception was a short “heat-wave” in mid-June, peaking on June 12, when the temperature reached 30.0 degrees – the warmest day of the summer.  The coldest temperature of the summer was just a few days earlier on June 9, when the overnight low hit 8.6 degrees.

Daily & Average Max & Min Temperatures, Summer 2019