May Outlook: Consistent warmth could be in jeopardy for these Canadians

A nice warm weekend is ahead, but most of the first half of May will still be below-seasonal.

After a cold April across most of Canada, many are looking forward to more consistent warm weather. Will May bring a change in the weather pattern? Please read on for details.

But first, let’s take a quick look back at a rather unusual April.

The map below shows just how unusually widespread the colder-than-normal weather was during April 2020. The various shades of blue and green show that most of Canada and even much of the United States were colder than normal. The coldest weather relative to normal was found across the Prairies. However, a map for a month as a whole overlooks some interesting details.


April actually started out warmer than normal across most of Ontario and Quebec. The map below shows temperature anomalies for the first two weeks of April. Meanwhile, the Prairies saw mid-winter cold and even record-breaking cold at times during the first half of April.


However, as we progressed through mid-April, the cold expanded east and the frigid pattern relaxed across B.C. and Alberta.


During late April, the colder-than-normal weather remained widespread across Canada, but the focus of the coldest weather shifted to Ontario and Quebec while parts of the southern Prairies saw a brief taste of late spring and even early summer-like weather.

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However, the first weekend of May will feature a much warmer pattern across the country. Most of Canada will see near-seasonal or even above seasonal temperatures, especially from Alberta to southern Quebec, where temperatures this weekend will reach the upper teens -- and a few places could even reach the lower 20s. Parts of southern Ontario could top 20°C on Sunday, but some lakeshore areas will be several degrees cooler.


However, the pattern change will be short-lived. On the map above you can see an area of chilly weather around Hudson Bay and that will plunge south for early next week. This will be the start of an extended period of colder-than-normal weather from the eastern Prairies to Atlantic Canada that will last through the Mother’s Day weekend and likely continue into the middle of May.


The coldest weather relative to normal will be centred on Ontario and Quebec. Fortunately, “normal” temperatures across the region during May are five to eight degrees warmer than they are during April. So, even with the chilly pattern, temperatures will still be noticeably warmer than the past few weeks.

Meanwhile, above-seasonal temperatures are expected to build across British Columbia and Yukon and then spread east at times into the western Prairies. Alberta and Saskatchewan will see back-and-forth swings in temperature which should tip to the warm side of normal across parts of Alberta, but temperatures will trend colder to the east.

During late May, we expect that the pattern will break down, with the chilly weather relaxing across the eastern half of Canada, and temperatures will trend closer to seasonal across Western Canada. Meanwhile, a much warmer pattern will develop south of the border and eventually we expect that warmth will spread into the Great Lakes and southern Quebec as we head into June.


However, there is still a lot of uncertainty regarding the timing for this pattern change. On occasion, pattern changes can occur rather abruptly, but more often than not they take longer to develop than expected. So, it is still too early to say whether the chilly pattern across Eastern Canada will relax around May 15-20, or if we will have to be patient and wait until the end of the month for more consistent warmth.