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A warm summer, but not record breaking

Was this summer the warmest in recent memory? Well, that depends how you define ‘summer’

This map shows the total amount of precipitation that fell across the Prairies this past summer (the 90-day period ending Aug. 27). It might be a little surprising to see that most areas saw normal to above-normal amounts.
I should point out that most of the rainfall came early in the summer, with conditions becoming progressively drier later in the summer, and that there were still large areas of the agricultural Prairies that did see below-normal to moderately low amounts of precipitation.

Well, summer is now officially over, so it is time to look back at the weather numbers and see just how warm and dry this summer has been. From a climatic or meteorological view, summer is three months long and encompasses the months of June, July and August. Just like winter, summer can be stretched to sometimes include May or September, depending on the weather. For this look back, I will look at each month from May through to August and then explore the true summer period (June through August), along with a longer summer period of May through August, because last May was so warm.

Starting off with a quick look back at August: even with some record-breaking heat early in the month, mean monthly temperatures across southern and central Manitoba were not as warm as we saw earlier this summer. The Winnipeg region was the hot spot, with a mean monthly temperature of 19 C, which is only 0.2 C above average. The Brandon region was the next warmest with a mean monthly temperature of 17.8 C or only 0.1 C above average. Finally, the Dauphin region was the cold spot, with a temperature of 17.2 C, which was actually 0.5 C below the long-term average. August was very dry across all regions, with Winnipeg reporting about 32 mm, Brandon 22 mm, and Dauphin a meagre four mm of precipitation. Overall, August came in with near-average temperatures and below-average rainfall. Looking back at the forecasts, it looks like Environment Canada gets the win with its call for near- to slightly below-average temperatures and below-average rainfall.

Now on to our look at the summer. Instead of just looking at mean monthly temperatures, I looked at the average-monthly high and low temperatures for each month and then combined them together to get mean-summer high and low temperatures for the periods of June to August and May to August. I did this for all of the major stations across the Prairies and it turned out that Manitoba saw the warmest temperatures this summer, followed by Saskatchewan and then Alberta. Since Alberta’s summer came in close to average, I am only going to include Manitoba and Saskatchewan’s values here (see Table 1 below).

Table 2 (see below), meanwhile, takes these values and compares them to their respective long-term averages, showing the difference from average. Looking at those values, you can see that this summer (June to August) was warmer than average by just over 1 C across Manitoba (mean temperature), cooling to around half a degree above average in Saskatchewan. If we include May temperatures, Manitoba jumps to about 1.5 C above average and Saskatchewan just over 1 C above average. What jumped out at me was the fact that daytime maximums were well above average for both the June-to-August period and the May-to-August period, but the overnight lows were only near to slightly above average. This goes against the trend we’ve seen over the last several years of warmer-than-average minimums and near-average daily highs.

One other statistic that I looked at was the number of days with maximum temperatures greater than 30 C. Table 3 (see below) shows the number of 30-plus C days for each month, the total, and the difference from the long-term average number of days. You can see that all areas saw a greater-than-average number of 30-plus C days, with the Manitoba locations seeing around double their usual amount.

How do these numbers compare to other years? Well, starting with the number of 30-plus C days, we only have to go back to 2011 to find similar numbers. The difference between this year and 2011 was the higher number of 30-plus C days in May and June of this year. The greatest number of 30-plus C days I could find occurred in 1936 when Winnipeg recorded 29 days, with a remarkable 13 days in a row in July of that year.

If we compare the overall maximum, minimum and mean temperatures for this summer to past years, the values for the June-to-August period don’t come close to any record values, with this summer coming in right around the same as the summer of 2011. When we add in the very warm May, then the values come a little closer to the record set in 1988, but still fall short by about a degree.

If you were to listen to most people talking about the summer weather, the general impression was that this has been one of the warmest summers in a long time. If we just look at the official summer period of June to August, then, while it was a warmer-than-average summer, it wasn’t that unique and we only have to go back to 2011 to find similar temperatures. If we include May, then it was a very warm extended summer and we must go back 30 years to 1988 to find a warmer period.

About the author

Co-operator contributor

Daniel Bezte

Daniel Bezte is a teacher by profession with a BA (Hon.) in geography, specializing in climatology, from the U of W. He operates a computerized weather station near Birds Hill Park.



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