Toronto · dissemination-area heat vulnerability
How a city heats up.
Heat sounds like something that falls on a city evenly: the same sun, over every block. In Toronto it settles heaviest where the trees have been cut down, where incomes are lowest, where residents are oldest, and where nobody can afford to keep the windows closed and the air conditioner running. The block you happen to live on already shapes how this summer will feel.
3,698 dissemination areas
Heat vulnerability, block by block
Source: Toronto Heat Vulnerability Index (PCA-derived), dissemination-area level, 2016 Census
Same map, three overlays
What drives the vulnerability score
A vulnerability score is an argument, a claim about which conditions matter and how much. Three of those conditions carry more weight than the rest: how much shade a block has, how much money its households have, and how old its residents are. The heat index underneath never changes. What changes is which argument the dots are making, and whether it lines up with the blocks already colored darkest red.
01
Less tree cover, more heat
A tree is a small, slow machine for cooling a city, pulling water up through its roots and releasing it as vapor over the pavement it shades. Where that machine was cut down decades ago for parking lots and wider roads, the block still pays for it every summer afternoon, in degrees.
02
Income shapes exposure
Air conditioning is a purchase before it is a comfort, and not every household can make it. Older buildings hold onto heat longer than new ones, and they tend to be where rent is cheapest. Income and heat risk end up describing nearly the same map.
03
Age changes the stakes
A young body sweats its way through a hot afternoon without much thought. An older heart and older lungs work harder to do the same job, and heat becomes a medical risk rather than an inconvenience. The same thermometer reading means something different depending on who is standing under it.
Tree canopy
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What the map adds up to
Toronto already knows where its next heatwave will hit hardest.
A city is made of its trees, its rents, its ages, its hospitals, and the roads between them, as much as its temperature. Layer those things together and Toronto already knows, block by block, where its next heatwave will do the most damage: the same places with the least shade, the lowest incomes, and the oldest residents also sit farthest from anywhere to cool off. As emissions keep climbing toward the scenarios above, that overlap is what will decide how the next heatwave unfolds, more than the number on the thermometer ever could.
Checking on an older neighbour during a heat warning, or knowing the nearest cooling centre before a hot day arrives, matters most in exactly the blocks this map colors darkest.