Where are the warmest and the coolest places in Montreal?
Parks with greenery and tree cover are shown to be the coolest places on this map
Summer means heat waves, and cities can get unbearably hot thanks to the urban heat island effect. The concentration of asphalt and concrete traps in heat, making urban centres significantly hotter than natural areas.
It's easy to see on a map. The Satellite readings from CERFO, a forestry research centre in Ste-Foy, Que., clearly shows which parts of Montreal are hotter relative to others.
The good news is that there are plenty of spots to escape the hot days.
Here are 13 sectors across the Island of Montreal that are both cool, and offer a vast swath of trees and activities during the hot summer months.
See a larger version of the map here
A quick warning: the map does not show exact temperatures, only relative differences. One cannot say, for example, that it's 32 C in a red zone or 25 C in a blue one.
3400 Blvd. des Trinitaires
Bois de Saraguay Nature Park
9150 Gouin Blvd. West, Cartierville
20800 Gouin Blvd. W., Pierrefonds
De la Promenade-Bellerive Park
9200 Notre-Dame Blvd. E.
St-Laurent Boulevard, Villeray
La Fontaine Park
Sherbooke Street East
4955 Côte-des-Neiges Blvd.
Mount Royal Park
Avenue du Parc
14912 Notre-Dame Blvd. E., Rivière des Prairies
5217 Lavoisier Blvd., Saint-Léonard
Quai-de-La Tortue Park
LaSalle Boulevard, Verdun
204 Belmont Ave., Pointe-Claire
William Cosgrove Centennial Park
3000 Lake St., Dollard-des-Ormeaux
Why is it so warm in the city?
The urban heat island effect is caused mainly by three features of cities:
- Low tree cover.
- Dark materials, like tar and asphalt that absorb sun rays and radiate heat.
- "Canyons" created by tall buildings that trap in heat.
Roofs made from dark materials and streets can reach temperatures as high as 80 C during very warm days, according to a report from the Institut national de santé publique du Québec.
Montreal can sometimes be 12 degrees warmer than surrounding rural areas due to a combination of these factors.
The number of days of extreme heat is also expected to spike due to climate changes, according to Natural Resources Canada. In Montreal, there are about nine days per year where the temperature is above 30 C. Natural Resources Canada predicts that by 2070, there could be as many as 27 days where the temperature breaks 30 C.
What can be done to reduce heat in urban centres?
There are many ways to mitigate heat islands. These include:
- Planting more trees.
- Adding vegetation to parking lots.
- Paving roads with light-coloured material.
- Covering building walls with plants like ivy.
- Green roofs or replacing dark roof material with light or reflective surfaces.
- Turning more alleys into green alleys (12 boroughs have specific plans on this).
The temperature map was created using data from CERFO, which used images from the SPOT-5 satellite and surface temperature readings from the Landsat-7 satellite. A total of 67 images were collected over six years, always during the summer months.
CERFO developed a mathematical model to combine surface temperatures from low resolution readings (100x100 metres per pixel) onto high resolution images without thermal data (20 metres).
The map does not show absolute temperatures, but relative temperatures in urban areas.
The prediction model has a margin of error between the real and predicted temperature. The overall accuracy was assessed at 67 per cent. CERFO believes that this margin of error of 33 per cent is satisfactory given the extent of the territory analyzed (all of urban Quebec), which has a wide variety of terrains, such as Montreal and Gaspé.
The data is published in the Quebec government's open data portal.
photos by Martin Thibault/Radio-Canada