A heat wave is brewing across Alberta, British Columbia and Saskatchewan this week, with temperatures forecast to top 30 degrees Celsius, triggering heat warnings as far away as the Mackenzie Valley in the Northwest Territories. With climate change, heat waves are becoming more frequent, but how normal is a heat wave at this point in the summer? And after last year’s deadly heat, how does this compare?
What’s behind this summer heat?
Heat is building under a ridge in the United States and is now pushing into Canada. As a strong area of high pressure builds to the west, temperatures are rising and will continue through at least the end of the weekend. Kyle Fougere, a meteorologist at Environment and Climate Change Canada, says the length of this heat wave is due to a pattern that has set up across the country, with high pressure and heat in the west and low pressure in the east. “Because there’s a bit of a blocking pattern with this strong low pressure system to the east, it’s going to last quite a while,” says Fougere. As our ridge of high pressure forms to the west, temperatures have a chance to get warmer and warmer, he says. “That heat is increasing day by day because these high pressure areas have sinking air. They have these clear skies. And so you just have a lot of days of clear skies and warming.”
Heat waves and climate change
We will have to get used to heat waves as we continue to feel the effects of climate change. While the frequency of colds is not as well known, our heat waves are becoming more frequent. According to the Intergovernmental Panel on Climate Change’s report on changes in climate extremes, the duration or number of warm periods or heat waves has increased since the mid-20th century. And this trend looks set to continue. “It is very likely that the length, frequency and/or intensity of warm spells or heat waves will increase over most land areas,” the report said. Youngsters try to beat the heat at an irrigation canal in Chestermere, Alta., Tuesday, June 29, 2021. (Jeff McIntosh/The Canadian Press)
A year after the deadly heat
As we see more frequent heat events with climate change, the question of severity comes into play, especially one year after the unprecedented June 2021 heat event. The 2021 heat dome led to the deaths of 619 people in BC, making it the deadliest weather event in Canadian history. It broke an all-time heat record for Canada as temperatures topped 40C. Fougere says it’s normal to think of heat events in the context of recent extremes. “This historic heat event last year is definitely on everyone’s mind because of all the impacts … the lives lost and the fires that started and all the records that were set,” he says. Despite that memory, Fougere says heatwaves like the one we’re seeing this week are normal. He says we might see some local records fall, but he doesn’t expect any all-time records to fall in Alberta. “A ridge of high pressure moving over Western Canada and lasting for several days bringing temperatures into the low 30s is extremely common.” This summer has been slightly unusual because it started out on the cool side, especially in Alberta. Fougere says July acted as a turning point. “From about mid-July is when we started to see temperatures pick up. We have a very different second half of summer.” And when it comes to August, Fougere adds that although average temperatures usually peak in July, temperatures of 30C are most common in August.
The heat makes fires more difficult to control
Heat waves can raise red flags when it comes to fire danger in Canada. So far this season, Saskatchewan has had 325 fires, on par with the five-year average. Alberta has seen 819 wildfires. Derrick Forsythe, a provincial information officer for Alberta Wildfire, says while there have been fewer fires so far this year compared to 2021, the area burned is larger. To date last year, 1,123 fires in Alberta had burned 53,920 hectares. This year, the province has seen 819 fires that have burned 107,517 hectares. A wildfire burning northwest of Nordegg, Alta., prompted an evacuation order for parts of Clearwater County in July. (Alberta Wildfire) Forsythe says fire danger varies depending on where you are in the province, as some areas have had more rain in recent days. This week, fire danger is high to extreme in the southern prairies and much of BC, moderate for much of northern Alberta and Saskatchewan, and elevated in the NWT Heat waves can increase the risk of wildfires and also make them more difficult to control. “If the temperature exceeds the relative humidity in an area, that means it’s really dry and it’s going to stay very dry,” Forsythe says. “If a fire starts, it’s going to burn very quickly and spread very quickly because it’s so hot and so dry. There’s no residual moisture … in the atmosphere or in the ground to moderate that spread.” Fire danger remains high to extreme in southern BC, Alta and Sask., while slightly lower further north. (Natural Resources Canada)
After the wave breaks
Fougere says heat waves like this can often be followed by another extreme: severe thunderstorms. “When we have that high-pressure break and that low-pressure system comes through, it’s able to harness all that heat and energy that’s built up and unleash those intense storms.” These storms can pose flooding risks, especially if the ground is extremely dry. Myles Dyck, a professor of soil science at the University of Alberta, says that in an extreme drought, the driest soils can become hydrophobic — resistant to absorbing water. “And if there is too much precipitation … depending on the topography of the surface, it will run to lower elevations,” he says. Although the south remains in drought conditions, the risk of soil becoming waterlogged is fairly low with this heat wave for the most part. Despite the lower risk, Dyck says there are ways to help your garden. “Keep mulch on your soil, either as a canopy of live vegetation or some type of mulch. This will definitely protect the soil from drying out.” Our planet is changing. So is our journalism. This story is part of a CBC News initiative called “Our Changing Planet” to show and explain the effects of climate change. Keep up to date with the latest news on our Climate and Environment page.
