Calgary's May long weekend weather is trash: A statistical analysis

CBC

17-05-2025

Queen Victoria was born before Canada became a country and died before Alberta became a province, but her legacy looms large in the form of a holiday that is held up to this day as the official kickoff to summer — even though it rarely delivers on that promise.
For Calgarians, that's not just local lore. It's science.
Historical weather records show, more often than not, the weekend weather is cool — or downright freezing — and rainy, if not snowy.
That's not to say it's always bad. There have been the occasional years when the weather gods, in their infinite caprice, smiled down upon the people and granted them three consecutive days of sun and overnight lows that didn't leave frost on their tent flaps.
But those tend to be the exception. The rule, generally, is much gloomier for those itching to finally get outdoors after the long, harsh winter.
For people looking to get outdoors in the higher altitudes of Banff and beyond, it's even more rare to feel that summery glow.
Looking at historical weather records for the three consecutive days that form the modern long weekend — that is, the Saturday, Sunday and penultimate Monday in May — we can see the disappointment in data.
In Calgary, which had 140 years' worth of records available, only 15 per cent of May long weekends saw the high temperature exceed 25 C.
The average temperature, meanwhile, was below 10 C on 45 per cent of weekends, while the low temperature was below freezing 34 per cent of the time.
Banff, which has temperature records for 132 May long weekends, was even cooler, with only five per cent seeing the temperature rise above 25 C at any point.
Nearly three-quarters of long weekends in Banff had average temperatures below 10 C, while 70 per saw freezing overnight lows.
Rain — or snow
Not only do May long weekends tend to be defined by cool temperatures, they also tend to be at least a little wet — or snowy.
On 61 per cent of May long weekends dating back to 1885, Calgary received a trace of precipitation (defined as 0.2 millimetres of rain or 0.2 centimetres of snow) or more.
Meanwhile, 31 per cent of weekends saw more than five millimetres of combined precipitation, and a quarter saw more than 10 millimetres, in total.
Banff saw rain or snow more often, with at least a trace on 76 per cent of weekends and more than five millimetres on 33 per cent.
It tended to see fewer heavy precipitation events, though, with only 16 per cent of weekends recording more than 10 millimetres, in total.
Outdoor enthusiasts hoping for three consecutive dry days were usually out of luck. Those occurred on only 39 per cent of weekends in Calgary and just 24 per cent in Banff.
At least it's not a flood? Or a blizzard?
This year, Victoria Day falls on Monday, May 19.
And, keeping with meteorological tradition, the three-day weekend in 2025 is again forecast to be cool and rainy, in both Calgary and Banff.
And, as much as we may justifiably complain, we should remind ourselves: it could be worse.
At least it's not 1902.
Over the three-day period ending on Monday, May 19, that year, Calgary received a staggering 81 millimetres of rain, according to Environment Canada records.
The Calgary Daily Herald newspaper described the storm as "one of the worst in the history of the West," flooding creeks and rivers, damaging bridges and washing out rail lines.
"The streets of Calgary were a sheet of water for most of the day," the newspaper reported. "Cellars were inundated and staid citizens were seen braving the downpour in slickers and waterproofs, digging trenches and ditches around their houses."
Mother Nature offered no reprieve the following year.
Over the three-day period ending on Monday, May 18, 1903, more than 67 centimetres of snow fell on Calgary.
The spring blizzard struck nearby areas even harder. A headline in the Daily Herald declared: "90,000 head of cattle perished in Montana storm."
"Ten feet of snow and four degrees below zero cause terrible loss," the news report added. "Trains move with difficulty."
Victoria Day, then and now
One important note about history and chronology: the historical-weather data analysis in this article used the May-long weekend dates that we are familiar with today.
On modern calendars, Victoria Day falls on the second-last Monday in May.
But it wasn't always like this.
The holiday was initially celebrated on Queen Victoria's actual birthday of May 24, meaning it could fall on different days of the week each year.
It wasn't until 1952 that the date was made to always fall on a Monday, ensuring a long weekend.
So, the blizzard Calgarians endured in 1903 didn't technically fall on a long weekend for them.
The law at that time called for Victoria Day to be celebrated on May 24 unless the date fell on a Sunday — which it did, in 1903 — so the holiday was actually celebrated on Monday, May 25, making it a long weekend the weekend after the blizzard.
According to Environment Canada's historical data, it also snowed that following weekend in Calgary.
Because, of course it did.