Get your fans ready! The next few days are likely to be very hot in southern Quebec, according to Environment Canada, which is predicting a heatwave early this week.
On Saturday, the federal agency issued a special weather statement for the Island of Montreal, warning of a “prolonged heat wave” starting Sunday. Environment Canada expects highs between 30°C and 32°C, with humidex reaching 40. The sweltering temperatures could last through Friday.
The south of the province has already suffered a heat wave this year, from June 18 to 20, recalls Dominic Martel, meteorologist at Environment Canada. According to the criteria used by the organization, the phenomenon is observed when temperatures are at least 30 °C during the day and 20 °C at night, for three consecutive days.
In addition, this year, “there have been two other episodes that have come close to a heat wave,” within one or two degrees at night, he explains. “This week, if the forecast materializes, we will have a second one.”
When the abnormal becomes the norm
“Statistically, we have a two out of three chance of having a heat wave every summer. On average, per summer, we have 0.68,” says Dominic Martel, who observes an upward trend in the number of heat waves observed each year. “If we look at the number of heat waves from 1970 to 2000, and then from 2000 to 2024, we would have an increase in the number of heat waves of 15% to 20%.”
That said, a better indicator of heat episodes would be the number of days above 30 degrees per year. For example, if a heat wave lasts 8 days, it counts as a heat wave, but it will be more overwhelming than if it lasts only 3 days, illustrates the meteorologist.
“The climatic normal for Montreal is to have 10.6 days above 30°C [annuellement]. This year, to date, we are at 12.” If Environment Canada’s forecast is correct for this week, we would therefore reach 15 days above the 30°C mark.
And it’s only July, Mr. Martel recalls. “It’s possible to have 30 degrees even at the beginning of September.”
Since 2001, the expert has recorded five years with 20 or more days of at least 30°C, while before the turn of the millennium, the phenomenon was anecdotal.