Urban Heat Island Effect in Canadian Cities: Why It’s Getting Hotter and How We Can Cool Down

Introduction

On a hot summer day in downtown Toronto, the urban heat island effect in Canadian cities becomes clear. Parks feel cooler, while busy streets trap heat.

Urban heat islands occur when city landscapes, filled with asphalt, concrete, and rooftops, trap heat. These surfaces absorb more sunlight than natural landscapes. As Canadian cities grow, the UHI effect is getting stronger. Climate change is making it worse, leading to higher energy use, health risks, and stress on the environment (Oke, 2017).

What Causes Urban Heat Islands?

Urban heat islands form when cities replace natural landscapes with heat-absorbing materials.

For example:

• Asphalt can reach up to 60°C in direct sunlight.
• Vegetation stays cooler because of shade and evapotranspiration (ECCC, 2020).
• Skyscrapers and tall buildings create “urban canyons” that trap heat.
• Cars, air conditioners, and factories add extra heat to the air.

In short, less greenery and more concrete means hotter cities.

The UHI Effect in Canadian Cities

The UHI effect is not limited to mega-cities. It is affecting Canadian municipalities across the country.

• In Montreal, urban areas can be up to 5°C warmer than rural areas during heat waves (Smargiassi et al., 2009).
• In Toronto, NASA satellite images reveal much higher temperatures in industrial and commercial districts (Voogt & Oke, 2003).
• In Vancouver, city planners found heat “hotspots” in areas with few trees and dense buildings. Low-income and elderly residents are most at risk (City of Vancouver, 2021).

These examples show that the UHI effect is already a daily reality in Canada.

Health and Environmental Impacts

The UHI effect is more than an inconvenience. It can be deadly.

• Hotter cities increase the risk of heat exhaustion, dehydration, and heat stroke (Health Canada, 2011).
• Seniors, children, and people without air conditioning face the highest risks.
• In the 2018 Quebec heat wave, 66 people died from extreme heat (ECCC, 2020).

Environmental damage is also significant. Cities require more electricity for air conditioning. If that energy comes from fossil fuels, greenhouse gas emissions rise. Local biodiversity also suffers as plants and animals struggle to survive in hotter conditions (Santamouris, 2020).

Climate Change and UHIs: A Dangerous Combination

Climate change is amplifying the UHI effect. Summers across Canada are becoming hotter and heat waves more frequent (Bush & Lemmen, 2019).Climate change is amplifying the UHI effect. As we explained in our article on climate change in Canada, rising average temperatures make heat waves more frequent and severe.

The combination of global warming and city heating creates compound heat extremes. These events can strain power grids, overwhelm hospitals, and increase deaths. Without urgent action, cities in Southern Ontario and Quebec will face dangerous levels of summer heat.

Solutions for Cooler Cities

1. Expanding the Urban Tree Canopy

Trees provide shade, reduce surface and air temperatures, and clean the air. Toronto’s long-term plan is to raise its tree canopy from 28% to 40% by 2050 (City of Toronto, 2018).

2. Green Roofs and Living Walls

Green roofs absorb less heat, improve insulation, and reduce flooding from stormwater. Toronto was the first North American city to pass a Green Roof Bylaw.

3. Cool and Reflective Materials

Using reflective roofs and light-colored asphalt lowers surface heat. Montreal is testing this method in city streets (Ville de Montréal, 2022).

4. Water Features and Blue Infrastructure

Ponds, fountains, and restored waterways cool the surrounding air through evaporation.

5. Community Cooling Centers

Public cooling centers give vulnerable residents a safe place during extreme heat.

Canadian Success Stories

• Vancouver has planted thousands of trees in heat-vulnerable neighborhoods.
• Montreal is replacing dark pavements with lighter, reflective surfaces and adding more parks.
• Toronto has built over 500 green roofs since its bylaw began, helping reduce both heat and flooding.

These real-life examples show that Canadian cities can fight the UHI effect with smart planning.

What Individuals Can Do

You do not need to wait for city governments to act. Homeowners and residents can help reduce urban heat too:

• Plant and care for trees or native plants.
• Use light-colored paint for roofs and driveways.
• Support local green planning initiatives.
• Drive less to reduce emissions and waste heat.

Even small actions add up when done by thousands of residents.

Conclusion

The urban heat island effect in Canadian cities is a growing challenge. It affects health, increases energy use, and worsens climate change.

However, solutions exist. By planting more trees, creating green roofs, using reflective materials, and opening community cooling spaces, cities can become cooler and safer.

With action from governments, communities, and individuals, Canada’s urban areas can adapt to climate change and remain livable for future generations.

References

Bush, E., & Lemmen, D. S. (2019). Canada’s changing climate report. Government of Canada. https://changingclimate.ca/CCCR2019/

City of Toronto. (2018). Strategic forest management plan 2018–2028.https://www.toronto.ca/data/parks/pdf/trees/sustaining-expanding-urban-forest-management-plan.pdf

City of Vancouver. (2021). Urban forest strategy update. https://vancouver.ca/parks-recreation-culture/urban-forest-strategy.aspx

Environment and Climate Change Canada. (2020). Urban heat island effect. Government of Canada. https://www.canada.ca/en/health-canada/services/environmental-workplace-health/reports-publications/climate-change-health/climate-change-health-adaptation-bulletin-number-1-november-2009-revised-december-2010-health-canada-2009.html

Health Canada. (2011). Heat alert and response systems to protect health: Best practices guidebook. https://www.canada.ca/content/dam/hc-sc/migration/hc-sc/ewh-semt/alt_formats/pdf/pubs/climat/response-intervention/response-intervention-eng.pdf

Oke, T. R. (2017). Urban climates. Cambridge University Press.

Santamouris, M. (2020). Cooling the cities, A review of reflective and green roof mitigation technologies to fight heat island and improve comfort in urban environments. Solar Energy, 103, 682–703. https://doi.org/10.1016/j.solener.2012.07.003

Smargiassi, A., Goldberg, M. S., Plante, C., Fournier, M., Baudouin, Y., & Kosatsky, T. (2009). Variation of daily warm season mortality as a function of micro-urban heat islands. Journal of Epidemiology & Community Health, 63(8), 659–664. https://doi.org/10.1136/jech.2008.078147

Ville de Montréal. (2022). Climate plan 2020–2030. https://montreal.ca/en/articles/montreal-climate-plan-objective-carbon-neutral-2050-7613

Voogt, J. A., & Oke, T. R. (2003). Thermal remote sensing of urban climates. Remote Sensing of Environment, 86(3), 370–384. https://doi.org/10.1016/S0034-4257(03)00079-8