Photo: OldYorkGuy · CC BY-SA 3.0A flood study covers Toronto: 4 on the national inventory, the newest from Toronto Regional Conservation Authority
Wildfire barely registers for Toronto, at 0% of the land within 25 km since 1986 (0.000% a year). Shaking is about as much of a worry in Toronto as in most places, at $0.043 a year per $1,000 of building value ($0.030 typical). Radon is lower than usual: 2.7% of tested homes in the survey area topped the guideline, against 6.6% for the typical town.
What stands out about Toronto’s hazards
Four national sources, each read for Toronto: earthquakes, radon, past fires and flood studies.
What Toronto faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
No Hazard risk grade for Toronto yet
The grade weighs Toronto’s seismic risk and radon equally, and wildfire is one-sided: a high band counts against a town, a low one earns nothing.
How sure: Earthquake losses are a model’s expectation over many years, not a forecast for any one. The radon share rests on 74 home tests in the survey area, so a few homes move it. Small fires and grass fires are largely missing from the national burned-area record.
Little of the land around Toronto has burned: 0% within 5 km, 0% within 25 km since 1986
Past fire around Toronto’s homes, from the national burned-area record, with the fuel within 5 km.
At 0.000% of the land a year, Toronto’s burn rate is in the low band; the typical Canadian town sees 0.000%.
Since 1986 the nearest fire to Toronto’s homes came within 5.5 km, never inside 5 km.
Little near Toronto’s homes can carry a forest fire; only 1.1% of the land within 5 km is forest fuel, and 4.1% within 25 km.
Shares of land within 5 and 25 km of populated blocks: burned at least once in 1986–2025 (CWFIS burned-area composite), forest fuel and grass (fire behaviour fuel types, 2026, 250 m grid).
Burn rate a year, towns in Ontario · highest of 872
To three decimals the burn rate around Toronto is zero, as for 639 of the 872 towns in Ontario, while Sioux Lookout reaches 0.16%.
Each bar: the yearly average share of land within 25 km of a town’s homes that burned, 1986–2025 (CWFIS); the seven highest towns of 2,500 people or more.
Only 7.5% of Canada’s 2,610 towns are above the low band, which holds 92%; Toronto, at a rounded zero, is far from them.
Bands of the yearly burn rate: low under 0.05%, moderate under 0.25%, high under 1%, very high 1% or more; towns of 2,500 people or more.
Fire danger and active fires (CWFIS)
Canadian Wildland Fire Information System: National Burned Area Composite 1986–2025 and fire behaviour fuel types (2026), Natural Resources Canada. Measured within 25 km and 5 km of each populated dissemination area; past fire, not a forecast.
4 flood studies cover Toronto, the newest from Toronto Regional Conservation Authority
What Canada’s Flood Map Inventory lists for Toronto: who studied flooding and where to see their maps.
Toronto Regional Conservation Authority and others have studied flooding in areas that include Toronto: 4 studies, the latest from 2021.
| Study | By | Year | Status |
|---|---|---|---|
| Toronto Floodline Consolidation | Toronto Regional Conservation Authority | 2021 | final |
| Rockcliffe Special Policy Area | Toronto and Region Conservation Authority | 2020 | final |
| Serson Creek | Credit Valley Conservation Authority | 2019 | final · not public |
| Lake Ontario Shoreline | Credit Valley Conservation Authority | 2005 | final · not public |
Towns with a flood study on file
Mapping in Ontario reaches 69% of towns, Toronto included, beside 58% across Canada.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
The studies touching Toronto lean recent: 2 of 4 date from the 2020s, the first from the 2000s.
Study dates as the NRCan inventory lists them, one count per study touching Toronto.
Flood is shown here, never graded: a study says where a map exists, not how many of Toronto’s homes stand in a flood zone.
The inventory’s own caution (NRCan): “The Canada Flood Map (CFM) does not include every flood hazard map in Canada and may be incomplete or contain inaccuracies. It should not be relied upon as the official source of flood mapping information. Furthermore, if a map appears to be missing, this does not necessarily mean that the area has never been mapped. For the official version of a map, updated information, or confirmation of applicable regulations, please contact the local authority responsible for flood mapping.”
Natural Resources Canada, Canada Flood Map Inventory; links go to each study’s owner.
Expected shaking damage in Toronto: $0.043 a year per $1,000
Expected yearly building losses from earthquakes, from Natural Resources Canada’s model.
Earthquake losses in Toronto, $0.043 per $1,000, are in line with the typical $0.030 (1.4 times).
Shaking damage a year per $1,000 of building value
Neither high nor low in Ontario: Toronto’s $0.043 sits by the median of $0.043, while Alexandria reaches $0.21.
NRCan seismic risk model (2022): mean yearly building loss per $1,000 of value; medians of towns of 2,500 people or more.
Toronto’s earthquake risk lands near the centre of Canada’s range; 36% of the 2,611 towns are higher.
Each column: the share of Canada’s towns of 2,500 people or more in that range of yearly loss per $1,000 (NRCan, 2022).
The loss is to Toronto’s buildings alone, from ground shaking; infrastructure and secondary hazards are left out.
Natural Resources Canada, Canada’s Seismic Risk Model (2022), by census subdivision (2016 boundaries; a few 2021 subdivisions take their residents’ mean).
Radon runs low around Toronto: 2.7% of tested homes over the guideline
Long-term radon tests in homes across the survey area, against Health Canada’s guideline. · Measured across the City of Toronto Health Unit: radon tests
At 2.7% over the guideline, the area around Toronto is under the typical Canadian town’s 6.6%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
The median in Ontario is 4% over 200 Bq/m³; around Toronto it is 2.7%.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
The quietest radon band, under 5%, holds 37% of Canada’s 2,611 towns and Toronto; 63% sit higher.
Each bar: the share of Canada’s towns of 2,500 people or more whose survey area had that share of tests over 200 Bq/m³.
Basements, soil and how a house is sealed decide its radon, so in Toronto only a test can say.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Weather and fire alerts for Toronto
Environment and Climate Change Canada issues the weather alerts for Toronto; Alert Ready carries the urgent ones to phones, radio and TV.
| Alert | What it means |
|---|---|
| Warning | Severe weather is happening or about to: act now. |
| Watch | Conditions favour severe weather: be ready. |
| Advisory | Weather that is less severe but could disrupt the day. |
| Special weather statement | Unusual weather worth knowing about. |
| Special air quality statement | Poor air, often wildfire smoke. |
In fire season, check CWFIS for danger and active fires around Toronto, and listen to local authorities for orders.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
How Toronto’s neighbours compare on hazards
Wildfire band, earthquake risk, radon and flood studies for each place nearby.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Toronto | Low | $0.043 | 2.7% | Yes |
| North Toronto 16,007 · 0.6 km | Low | $0.043 | 2.7% | Yes |
| Mount Pleasant East 16,373 · 1.0 km | Low | $0.043 | 2.7% | Yes |
| Bridle Path-Sunnybrook-York Mills 9,909 · 1.2 km | Low | $0.043 | 2.7% | Yes |
| Lawrence Park South 15,018 · 1.4 km | Low | $0.043 | 2.7% | Yes |
| South Eglinton-Davisville 23,380 · 1.5 km | Low | $0.043 | 2.7% | None listed |
| Yonge-Eglinton 12,424 · 1.5 km | Low | $0.043 | 2.7% | Yes |
Bridle Path-Sunnybrook-York Mills burns a little more than Toronto, in the same low band (low here).
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Toronto faces
What to do about the hazards Toronto faces, and what to ask before you buy.
- Test for three months in winter.
- Over 200 Bq/m³: fix it.
- Kits are cheap; pros test too.
- Never drive through floodwater.
- Move papers and medicines upstairs.
- Ask whether your street is mapped.
- Clear needles and wood nearby.
- Keep a grab-and-go bag ready.
- In smoke, stay in; filter air.
- Has it had a radon test?
- Check the address on the flood map.
- Are flood and wildfire insured?
What this data can and can’t tell you
- Radon is a survey. About 14,000 homes were tested across Canada in 2009–2011, and the share over the guideline for Toronto is its health region’s, the survey’s design unit.
- Flood studies aren’t flood zones. NRCan’s inventory says where flood mapping exists, not where water goes; the map’s owner is the authority for Toronto.
- Wildfire counts one way. Wildfire is read from the national burned-area record around Toronto’s homes since 1986, a history of fire that may lower Risk but never raises it.
- Earthquakes are modelled. NRCan models what earthquakes would cost buildings each year on average, subdivision by subdivision; Toronto’s figure is its subdivision’s.
Questions about flooding and hazards in Toronto
Is radon a problem in Toronto?
Around Toronto, 74 survey homes were tested and 2.7% came in over 200 Bq/m³, a guide to the area, not to any one home.
Is Toronto at risk of wildfire?
Fire has reached 0% of the land around Toronto since 1986 (last in 2001); at low, it neither helps nor hurts the grade.
Does Toronto flood?
There is flood mapping for Toronto on the national inventory, each study linked to its owner’s map, none of them graded.
How big is the earthquake risk in Toronto?
In NRCan’s seismic model, Toronto’s buildings lose $0.043 per $1,000 of value in an average year.
How is Toronto’s Hazard risk Grade worked out?
The grade is still to come for Toronto, and it will weigh seismic risk and radon, with a one-sided wildfire input.
Seismic risk: Natural Resources Canada. Radon: Health Canada. Wildfire: Canadian Wildland Fire Information System. Flood studies: Natural Resources Canada, Canada Flood Map Inventory. Contains information licensed under the Open Government Licence – Canada.
Sources: NRCan, Canada’s Seismic Risk Model 2022 · Health Canada, Cross-Canada Survey of Radon Concentrations in Homes · CWFIS, National Burned Area Composite and FBP fuel types · NRCan, Canada Flood Map Inventory. Under the Statistics Canada Open Licence.
Adapted from Statistics Canada (Census of Population 2021, population estimates 2025, 2021 census boundaries) under the Statistics Canada Open Licence; this does not constitute an endorsement by Statistics Canada. Neighbourhood names in some cities © OpenStreetMap contributors (ODbL).