Does a May heat wave indicate a scorching summer ahead?
Summer-like heat in May could portend a steamy summer across Quebec
We’ve seen some hot temperatures across Quebec this week, where readings soared to 30°C in some locations even though it’s only the middle of May.
This summer-like heat in spring could be a sign of things to come—and data from past years with similar setups paints an interesting picture for Quebec’s summer ahead.
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Does a May heat wave portend a hot summer?
Have you noticed that heat waves in May seem to be occurring more frequently and earlier than usual in recent years?
If so, you’re not dreaming! Summertime heat settles in quietly before summer actually arrives. That’s what we’ve seen this week with temperatures at or around 30°C in some regions.
Quebec experiences an average of four heat waves each year. A heat wave is defined as three consecutive days with temperatures at or above 30°C.
Since 2010, every time a heat wave has occurred in May, six of the summers turned out to be scorchers with the number of heat waves equal to or greater than normal. The only exception was 2022. The years 2016 and 2018 were particularly hot, with almost twice as many heat waves as the annual average.
Given the evidence from previous years, we can conclude that a heat wave in May is generally a good indicator that the summer will be rather hot.
Looking forward to what conditions you might expect this summer? Check back for the release of our summer forecast on Wednesday, May 28, for all the latest across Quebec and the rest of Canada.
Heat domes are the key to a hot summer
What makes for a hot summer? Another key element is the presence of a heat dome. There’s a good chance of a hot summer if this pattern builds before the season officially arrives.
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Heat domes form when a vast region experiences dry conditions. Dry soils evaporate little water into the atmosphere. This dry regime is amplified by the presence of a centre of high pressure characterized by sunshine, further drying out the soil. This feedback cycle heats up the atmosphere and contributes to hot summertime weather.
On the bright side, there’s less humidity
The good news, if you’re not a fan of muggy weather, is that this is still a relatively dry heat.
There’s less humidity across Quebec in May than there is in the summer. Vegetation is only just starting to grow and bodies of water are still pretty cold, so they evaporate less water into the atmosphere.
Initial bouts of hot weather like we’ve seen this week are less moisture-intensive, so a 30°C high in May exerts less stress on the body than the same temperature would during the middle of July.
Humidity around this time of the year has to travel into Quebec on southerly or southwesterly winds. In July, however, that humidity is already present and locked over the province. It’s this humidity that’ll determine our perception of a sweltering or scorching summer.
This article was translated and adapted from an article published by MétéoMédia, The Weather Network's Quebec-based sister station.
Header image created using imagery and graphics from Canva.