Saturday, June 3, 2023

Spring 2023 was dry and sunny, with overall normal temperatures

 Meteorological spring is from March 1 to May 31.  Overall, spring 2023 saw close to normal temperatures, but was much drier than normal.  

The mean temperature at Victoria Gonzales this past spring was 10.1 degrees, which is right on the 30-year average.  The average daily maximum for spring 2023 was 13.6 degrees , while the average daily minimum was 6.5, again both very close to the 30-year averages.  This masked some significant differences during the season.  March was 0.6 degrees C below normal, while April was a chilly 1.2 degrees C below normal.  That contrasted with May, which was the warmest May on record at Victoria Gonzales, a full 1.7 degrees C above normal.



The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales during spring 2023, compared with the 30-year averages.  Temperatures during March were fairly close to normal, then during April they fell significantly below normal.  There was a spike in temperatures in late April, with temperatures getting into the low 20s, then an even bigger spike in mid-May, with temperatures reaching the low 30s.  Temperatures remained above normal for most of May.  The warmest temperature was 30.7 C on May 14.  In fact, this was the second highest temperature ever recorded at Victoria Gonzales in May.  The coldest temperature was 0.4 C on March 1.  There were no days below freezing during spring 2023.  Normal is 0.7 days.

Daily Max & Min temps vs 30-yr normal, Spring 2023




Following a drier than normal winter, Victoria experienced a dry spring in 2023.  There was 58.4 mm of rain, just over half of the normal 115.4 mm 

There were just 22 days with measurable rainfall during spring 2023, compared with the normal of 33 days.  There were 8 days in March (normal 14.5), 11 days in April (normal 10.3), and 3 days in May (normal 8.4).  The wettest day was May 5, when 12.4 mm of rain fell.

The chart below shows daily precipitation during spring 2023, and compares the cumulative precipitation with the 30-year average.  Precipitation tracked below average throughout the spring.  







Overall, spring 2023 was sunnier than normal.  March saw more sun than normal, while April saw less.  However, May was likely one of the sunniest Mays on record in Victoria, with an estimated 335 hours.  The official record is 356.4 hours from May 1963.  There were 40 mostly sunny days during spring 2023, including 22 mostly sunny days in May.




Wednesday, May 31, 2023

A strong rainshadow and a dry April

Victoria is often in the rainshadow of the Olympic Mountains, and as a result it generally gets much less rain than surrounding areas.  This phenomenon was really on display in April.

Below is the radar image for April 6, 2023.  The rainshadow "hole", to the northeast of the Olympic Mountains is clearly visible.  

Here is another radar image from April 6, showing a closer view of Victoria.  A great rainshadow, extending across Greater Victoria, the San Juan Islands, and over towards Anacortes.


Southwestern B.C. and the US Pacific Northwest experienced an atmospheric river event from April 6-9, 2023.  However, the rainshadow kept Victoria extraordinarily dry.  Below is a chart comparing the rainfall totals for April 6-9.  Rainfall in the core area of Greater Victoria ranged between 0.8  and 2 mm.  Victoria Airport (located 25 km to the north and typically less protected by the rainshadow) received 8.3 mm.  Other locations in the region received 25 mm or more, including 64 mm at Vancouver Harbour and 77 mm at West Vancouver - nearly 100 times as much rain as the University of Victoria received.


While the April 6-9 event was the most dramatic, Victoria stayed significantly drier than other locations in the region for the whole month.  The chart below compares April rainfall totals.  Again, locations in the core area of Greater Victoria were much drier, receiving between 17.8 mm and 22 mm of rain for the entire month (normal April rainfall for Victoria Gonzales is about 34 mm).  The Victoria Airport and the Cowichan Valley each received more than 3 times as much rain as Victoria Gonzales.  Seattle received more than 5 times as much rain as Victoria, and Vancouver Harbour received nearly 9 times as much rain.   Port Alberni and West Vancouver received 11-12 times as much rain as Victoria Gonzales.

April continued the trend of a dry start to 2023.  During the first 4 months of the year, Victoria Gonzales has only received about 128 mm of precipitation - half of the normal 257 mm for that period.

Tuesday, March 21, 2023

Winter 2022-23 was colder and drier than normal

Meteorological winter is from December 1 to February 28.  Winter 2022-23 was colder and drier than normal.  

The mean temperature at Victoria Gonzales this past winter was 4.9 degrees C, compared with the 30-year average of 5.8 C.  The average daily maximum temperature was 7.0 C (versus normal 7.9 C), while the average daily minimum was 2.8 C (versus the normal 3.7 C).  December was much colder than average.  January was slightly milder than average, while February was colder than average.



The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales during winter 2022-23, compared with the 30-year averages.  The cold snap in late December really stands out, with temperatures far below normal. The temperature dropped as low as -9.5 C on December 22, the second December in a row with a very strong cold snap and very low temperatures. January temperatures were a bit above normal, but February temperatures once more fell below normal.

Daily Max & Min temps vs 30-yr normal, Winter 2022-23





Winter 2022-23 was drier than normal, with 197 mm of precipitation versus the normal of 266 mm. Precipitation was a bit above normal in December (114 mm vs. 98 mm), but January was very dry (26.3 mm vs. normal 104.3 mm), and February was also slightly drier than normal (57.1 mm vs. normal 63.5 mm).

The chart below shows daily precipitation during winter 2022-23, and compares the cumulative precipitation with the 30-year average.  Precipitation tracked close to average during the first part of the winter, but fell below average in January.  




Winter 2022-23 was also much snowier than normal.  There was 41 cm of snow compared with the normal 14 cm.  Nearly all of the snow (37 cm) fell in December.  

Monday, January 2, 2023

Victoria's weather in 2022

 

After a year of extremes in 2021 (including the hottest temperature on record and the most annual precipitation on record), 2022 was not quite so extreme.

The mean temperature for 2022 (10.5 C) was slightly below the 30-year average of 10.7 C, while the annual precipitation of 658.5 mm was very close to the average of 656 mm.

Victoria experienced the warmest late summer/early fall on record in 2022.  August and October were both the warmest on record, while September was the second warmest. Overall, the August to October period was 1.7 degrees warmer than the 30-year average.  

March, June, and July were slightly above normal.  The remaining six months were all below normal temperatures.  In particular, April-May was 1.8 degrees below normal and November-December was 2.1 degrees below normal, making for a cold spring and a very cold late fall/early winter.


The hottest temperature of 2022 was 30.9 degrees on June 26.  There were 2 days in 2022 with daily maximums above 30 C, compared with the normal of 1.1 days.  There were 18 days with daily maximums above 25 degrees, double the average of 9.1 days.    

The coldest temperature of 2022 was -9.5 C on December 21.  For the second winter in a row, Victoria experienced a significant cold snap in 2022, with 4 consecutive days below freezing.  Prior to 2021, Victoria hadn't experienced such a long cold snap for 36 years (since November 1985).  There were 19 days in 2022 when the temperature went below 0, significantly higher than the long-term average of 9.5 days, and the most since 1996.  Of those days when temperatures dropped below freezing, 12 occurred in November and December.

The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales in 2022, compared with the long-term normal temperatures.  The chart shows a cold snap in late February, and the cool spring,
 with highs consistently below normal from mid-April to the end of May.  This was followed by a short heat wave in late June, then fairly consistently above-average temperatures from August to October.  There was an abrupt shift to below normal temperatures in November and December, culminating in the severe cold snap in late December.




The chart below shows daily and cumulative precipitation at Victoria Gonzales for 2022.   The thing that really stands out is the extraordinary 3-month dry spell from July 19 to October 20. During that period there was just 0.6 mm of rain recorded at Victoria Gonzales, making it the driest 3-month period on record, not just for Victoria, but likely for any major Canadian city.  The remainder of the year saw 3 wet periods (October 21-November 8, November 22-30, and December 17-31).  These were separated by two unusually dry spells for what is typically the wettest time of year in Victoria: just 2 mm of rain over weeks from November 9-21 and just 12 mm during the first half of December.





There were 124 days with measurable precipitation in 2022, compared with the normal of 132 days.  The wettest day was October 30th, with 40.6 mm of rain.  There were 4 days with more than 25 mm of rain in 2022, a little above the average of 2.9 days annually.  

The chart below compares annual precipitation at Victoria Gonzales in 2022 with other locations in the region.  Thanks to its rainshadow location, Victoria is typically drier than most other locations, and that was the case once again in 2022.  However, while Victoria's annual precipitation was close to the 30-year average, it was below average at the Victoria Airport (90% of normal) and Vancouver (89% of normal), but slightly above normal in Seattle (103% of normal).  

2022 Annual Precipitation vs normal



Victoria received 54 cm of snow in 2022, more than triple the average of 16 cm, and the most snow in a calendar year since 1996.  (2021, with 44 cm of snow, was the second snowiest year in Victoria since 1996.) 


Friday, December 30, 2022

How much and how often does it snow in Victoria?

Victoria gets less snow than any other city in Canada.  The 30-year (1991-2020) average annual snowfall for Victoria is 16 cm.  That's significantly less than nearby Vancouver, which receives an annual average of 34 cm, as measured at the Vancouver Airport.  

The core area of Greater Victoria also gets significantly less snow than outlying areas such as Langford or the Saanich Peninsula.  The Victoria Airport, located 25 km north of Victoria, averages 34.8 cm of snow annually - more than double what the City receives.  It's quite common for there to be snow in the Westshore or the Saanich Peninsula, while there is little or no snow in the core area.  This is due to the generally milder temperatures near the Strait of Juan de Fuca and the lower precipitation amounts in the core thanks to the Olympic Mountain rainshadow.

The table below summarizes the average snowfall and snow cover (days with at least 2 cm of snow on the ground) in Victoria, by month.  December has the highest amount of snowfall (6.3 cm), although both December and January have on average, a similar number of days with snow on the ground (1.2-1.3 days).


While the table above shows the 30-year averages for snow in Victoria, there is a lot of variability from year to year.  The chart below shows the annual winter snowfall over the past century.  The chart shows 3 years (1949/50, 1968/69, and 1996/97) when Victoria received more than 100 cm of snow.  In fact, the snowiest winter on record for Victoria was 1915/16 (not shown on the chart) when Victoria received an astonishing 195.6 cm of snow!  On the other hand, there have been 7 winters in the past 125 years (6%) with no snow, and 33 winters (26%) with less than 5 cm of snow.  

The chart also shows the rolling 30-year average snowfall and 30-year median snowfall (starting with the 30-year period from 1898/99 to 1927/28 and finishing with the most recent 30-year period of 1993/94 to 2022/23).  Because the average snowfall tends to be skewed by the occasional large snowfall, the median snowfall (11.5 cm for 1991-2020) is lower than the average snowfall (16.0 cm). 


Even the 30-year average snowfall has fluctuated significantly over time.  From a low point of 19.9 cm for 1918/19 to 1947/48, the 30-year average snowfall reached a high point of 37.5 cm for 1946/47 to 1975/76.  Since then, average snowfall has generally been decreasing, with climate change likely contributing to this trend.  For the most recent 30-year period (1992/93 to 2021/22), snowfall averaged 17.4 cm (slightly higher than the 1991-2020 average).  

The chart below shows the trend in number of days annually with at least 2 cm of snow on the ground.  Snow on the ground has only been measured in Victoria since 1955, so the period of record is shorter.  As with snowfall totals, the days with snow on the ground varies considerably from year to year.  In 19 of the past 68 winters (28%), there have been no days with 2 cm or more snow on the ground.  On the other extreme, there have been 4 winters with more than 15 days with snow on the ground - including one winter (1968/69) when there was 30 days with snow on the ground!  The average number of days with snow on the ground has generally decreased over time, from about 5 days for the 1955/56 to 1984/85 period down to about 3.8 days for the most recent 30-year period (1992/93 to 2021/22), which again was slightly higher than the 1991-2020 average.



Another way to look at the snowfall data is to use quintiles.

  • The bottom quintile (the 20% of winters with the least snowfall) had an average snowfall of 1.2 cm and 0 days with snow on the ground.

  • The next quintile averaged 7.3 cm of snow and 0.7 days with snow on the ground.

  • The middle quintile averaged 16.5 cm of snow and 3.0 days with snow on the ground.

  • The next quintile averaged 30.3 cm of snow and 5.4 days with snow on the ground.

  • The top quintile (the 20% of winters with the most snowfall) had an average of 73.9 cm of snow and 15.2 days with snow on the ground.

You sometimes here about a big snow storm in another city dumping "a month's worth of snow" in a day or two.  Because snow is so infrequent in Victoria, it's not only very common to get a month's worth of snow all at once, but it's also common to get a full season's worth of snow in one storm.  For example, over the past 30 years, Victoria has received 76% of its total winter snowfall in a single two-day period.  During nearly one third of those years, Victoria received more than 95% of its seasonal snowfall in a single storm.

Other locations in the region have also seen a decline in average snowfall over the past few decades.  The chart below compares the trend in 30-year average snowfall in Victoria with other nearby locations (starting with the 30-year period from 1941/42 to 1970/71 and ending in the most recent 30-year period of 1993/94 to 2022/23).  All the locations have declined over this period.  Average snowfall levels in Victoria have trended quite closely to the pattern for Seattle.  By contrast, the Victoria Airport (in North Saanich) and the Vancouver Airport have significantly higher average snowfall levels, but they have also followed a declining trend.  




Tuesday, December 13, 2022

Fall 2022: an abrupt shift from warm and dry to cool and wet

 Meteorological fall is from September 1 to November 30.  Fall in Victoria nearly always transitions from warm and dry in September to cool and wet in November, but in 2022 the transition was very abrupt.  

Overall, the mean fall temperature at Victoria Gonzales was 11.8 degrees, which is 0.6 degrees warmer than the 30-year average.  September was the second warmest on record at Victoria Gonzales, while October was the warmest on record (2.2 degrees above normal).  However, November was tied for the 5th coldest on record (2.1 degrees below normal).  

The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales during fall 2022, compared with the 30-year averages.  From September 1 to about October 20, temperatures were consistently above normal.  There was then an abrupt shift, with temperatures much cooler than normal for the remaining 6 weeks of fall.  This included two brief cold snap, in early November and again in late November, when overnight temperatures dipped below freezing.

Daily Max & Min Temperature at Victoria Gonzales

Victoria typically experiences 9.7 days each fall when the maximum temperature exceeds 20 C.  In 2022, there were 25 such days.  Victoria usually only averages 1.5 days each fall when the maximum temperature exceeds 25 C.  In 2022, this occurred on 4 days this fall: Sept. 6th, 9th and 10th, and again on October 2nd. The maximum temperature this fall was 25.8 C on September 10th.

On the other hand, Victoria typically only experiences 0.9 days each fall when the overnight low temperature falls below freezing.  In 2022, there were 4 such days, the coldest being -2.2 C on November 29th.  


Victoria received 167 mm of rain from September to November, 26% less than the 30-year average fall rainfall of 227 mm.   

Victoria had 23 days with measurable rainfall this fall, well below the normal 37.8 days.  There was no measurable precipitation from September 1 to October 20.  Then 9 of the last 11 days in October had rainfall, followed by 14 days in November.   Normally, Victoria averages 7.8 days with measurable rain in September, 12.8 days in October, and 17.4 days in November.  


The chart below shows daily precipitation during fall 2022, and compares the cumulative precipitation with the 30-year average.   The fall started off extremely dry, with no measurable rain until October 21.  A rainy spell in late October/early November meant that fall rainfall was almost normal by November 7.  This was followed by another dry spell (a two-week period with only a few days of very light rain, less than 1 mm), before rain returned at the end of the month.  The wettest day of the fall was October 30th, with 40.6 mm of rain.  

Daily & Cumulative Precipitation at Victoria Gonzales

There were also two short periods of light snow in Victoria during November.  On November 7th, there was 2 cm of snow and on November 29th, there was another 1 cm of snow that quickly turned to rain and melted by noon that day.

Friday, October 21, 2022

An extraordinary drought

 Victoria is known for its summer droughts.  It is the driest major city in Canada - by far - during the summer months, with an average of 47 mm of rain during June to August combined.  It is also common to get long stretches with little or no rainfall during the summer.  On average, Victoria gets 31 consecutive days with no measurable rainfall each summer, and 42 consecutive days with less than 1 mm of rainfall.

However, the past three months have really been extraordinary.  From July 19 to October 20 - a period of 94 days - there have only been 3 days each with just a barely measurable 0.2 mm of rain (August 10, September 4, and September 28) at Victoria Gonzales.  That's a total of just 0.6 mm of rain in the past 3 months!  The nearby weather station at the University of Victoria has been even drier, with just 0.4 mm of rain over the same period.

This has been the driest 90-day period ever recorded at Victoria Gonzales, as shown in the chart below, easily beating the old record of 2.8 mm, from May 25 to August 22, 1951.  Note that most of these record dry periods tend to be centered on July and August, the two driest months in Victoria.  However, 3 of the 11 driest periods, include this year's, have extended into mid-October.


This record-breaking drought has not just impacted Victoria; it has affected all of southwestern B.C.  The chart below shows the total rainfall for various locations in southern B.C. over the past 3 months. As is often the case, Victoria has been the driest location, but most locations have been extraordinarily dry.  Keep in mind, that normal rainfall during this period is 91 mm at Victoria Gonzales and 231 mm at Vancouver Harbour.  


Not only has this period been the driest 3-month period ever recorded in Victoria (with 120 years of record-keeping at Victoria Gonzales), but it is also likely the driest 3-month period ever recorded in any major Canadian city.  The driest 3-month period ever recorded for some other Canadian cities includes 1.3 mm for Edmonton, 2.9 mm for Calgary, 6.1 mm for Vancouver Airport, and 37.9 mm for Toronto

In addition to being dry, it has also been a very warm 3 months.  The chart below shows the daily maximum and minimum temperatures at Victoria Gonzales during the drought period (July 19 to October 19), compared with the 30-year average.  With just a few exceptions, temperatures have been above normal.  The average daily maximum temperature for the period was 21.3 C -  nearly 3 degrees above the historical average of 18.4 C.  In addition, the average daily maximum temperature for the period in 2022 (21.3 C) is more than 1 degree warmer than the previous highest average maximum of 20.1 C for the same period in 1998.

Victoria Gonzales Daily Max & Min vs. normal