Edmonton ‘urban heat islands’ have significantly higher temperatures than surrounding rural areas: study

A new study out of the University of Alberta has revealed that Edmonton has “urban heat islands” (UHIs) where temperatures are significantly higher than surrounding rural areas in both the summer and winter.

The research released Wednesday shows surface temperatures in Edmonton have increased by as much as 12 C in the last two decades, compared with surrounding rural areas.

Led by Nilusha Welegedara and Sandeep Agrawal in the U of A’s Faculty of Science, the research focused on whether winter cities like Edmonton experience pockets of extreme heat typically more common in tropical countries.

To study UHIs in Edmonton, Welegedara analyzed satellite images taken year-round between 1999 and 2021 and considered 402 neighbourhoods, including industrial areas, residential areas, the river valley and Anthony Henday Drive.

Surface temperatures in Edmonton have jumped between six and 12 degrees overall compared with rural areas over the past 20 years, according to the research.

“UHIs exacerbate the impact of heat waves, going beyond the comfort zone of humans,” said Welegedara, a post-doctoral researcher at the university. “With more intensive and frequent heat waves, extreme heat is likely to increase over the next few years, so it’s important to increase public action to deal with the UHI phenomenon.”

The hot spots are at their most intense during the summer. They are caused by the loss of trees and other vegetation to urban development.

Welegedara found north Edmonton and some downtown areas with low vegetation had higher temperatures than south Edmonton. Due to the use of asphalt and concrete, built-up areas like buildings, roads, parking lots, sidewalks and rooftops contribute to higher surface temperatures. These materials absorb and store up the sun’s heat, then release it slowly, keeping temperatures high.

High-density populations and dwellings, road networks and average daily traffic volumes also led to UHIs.

The south side of Edmonton is considered cooler because of the river valley and older neighbourhoods with large boulevard trees, the study found.

Higher urban temperatures can lead to things like heat stroke or heat exhaustion, according to the study. This can lead to heightened health risks for vulnerable people.

1:37 The growing need to keep cities cool

Researchers say overall, the findings show winter cities like Edmonton need to pay close attention to the rise in UHIs and they should be included in their planning.

“While cities like Edmonton have long focused on their identities as winter cities, I believe Edmonton’s identity is changing as the temperature rises over the years,” Agrawal said. “that means planners need to actively account for both extreme winter and hot summer conditions in their policies, plans and guidelines.”

Ways to help east hotspots include planting more urban forests, retaining mature trees during development and infill projects and increasing vegetation cover, particularly in industrial and commercial areas.