Few places are as safe from hazards as Thornhill Woods: it beats 90% of Canadian towns
The burned-area map is nearly blank around Thornhill Woods, 0% within 25 km since 1986, 0.000% a year. Earthquake risk in Thornhill Woods is ordinary: NRCan’s model puts building losses at $0.028 a year per $1,000 of value, close to the typical town’s $0.030. Fewer homes than usual carry radon here, 0% over the guideline where the typical town has 6.6%. Thornhill Woods grades A for hazard risk; wildfire is low here, so it earns no credit.
What stands out about Thornhill Woods’s hazards
Four national sources, each read for Thornhill Woods: earthquakes, radon, past fires and flood studies.
What Thornhill Woods faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Thornhill Woods grades A for hazard risk
The grade weighs Thornhill Woods’ seismic risk and radon equally, and wildfire is one-sided: a high band counts against a town, a low one earns nothing.
Its place: #74 of 866 in Ontario and #383 of 2,589 Canadian towns.
How sure: Earthquake losses are a model’s expectation over many years, not a forecast for any one. Small fires and grass fires are largely missing from the national burned-area record.
Few fires near Thornhill Woods: 0% within 5 km, 0% within 25 km
Past fire around Thornhill Woods’ homes, from the national burned-area record, with the fuel within 5 km.
At 0.000% of the land a year, Thornhill Woods’ burn rate is in the low band; the typical Canadian town sees 0.000%.
Land that isn’t forest covers nearly all the ground around Thornhill Woods: forest fuel is 0.7% within 5 km and 3.8% 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 871
Near-zero burning puts Thornhill Woods with 638 of the 871 towns in Ontario, far below Sioux Lookout at 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.
Thornhill Woods shares the low band with 92% of Canada’s 2,610 towns, its burn rate rounding to nothing; 7.5% burn faster.
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.
Toronto Regional Conservation Authority has mapped flooding for Thornhill Woods (1 study)
What Canada’s Flood Map Inventory lists for Thornhill Woods: who studied flooding and where to see their maps.
One study on the inventory touches Thornhill Woods, Toronto Regional Conservation Authority’s from 2021, and its area can be large, so it says a map exists, not that the town floods.
| Study | By | Year | Status |
|---|---|---|---|
| Toronto Floodline Consolidation | Toronto Regional Conservation Authority | 2021 | final |
Towns with a flood study on file
Thornhill Woods is one of the 69% of towns in Ontario with a flood study on file; across Canada it is 58%.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
The grade leaves flood out, since a study area says nothing about how many of Thornhill Woods’ homes are at risk.
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.
Ordinary seismic risk in Thornhill Woods: $0.028 per $1,000 of buildings a year
Expected yearly building losses from earthquakes, from Natural Resources Canada’s model.
Thornhill Woods’ $0.028 is close to the typical town’s $0.030 (0.9 times as much).
Thornhill Woods shares its earthquake risk numbers with the rest of the city of Vaughan.
Shaking damage a year per $1,000 of building value
At $0.028, Thornhill Woods is below the typical town in Ontario ($0.043); Alexandria is highest at $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.
Around half of Canada’s 2,611 towns expect more shaking damage than Thornhill Woods (51%).
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).
Roads, pipes and bridges aren’t in Thornhill Woods’ figure, nor landslides or tsunami: it is buildings and shaking.
Natural Resources Canada, Canada’s Seismic Risk Model (2022), by census subdivision (2016 boundaries; a few 2021 subdivisions take their residents’ mean).
Little radon around Thornhill Woods: 0% of area homes over the guideline
Long-term radon tests in homes across the survey area, against Health Canada’s guideline.
Fewer homes than usual test high around Thornhill Woods: 0% against 6.6% for the typical Canadian town.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Radon runs lower around Thornhill Woods than in most towns in Ontario: 0% against 4%.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
Radon rarely tops the guideline around Thornhill Woods, as for 37% of Canada’s 2,611 towns; 63% see more.
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.
One home in Thornhill Woods can be high while next door is low; a three-month test settles it.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011). · Radon tests published for the York Regional Health Unit, not by town
Weather and fire alerts for Thornhill Woods
Environment and Climate Change Canada issues the weather alerts for Thornhill Woods; 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. |
For fires near Thornhill Woods, the national fire information system maps danger and active fires daily; local authorities give any evacuation order.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
How Thornhill Woods’ neighbours compare on hazards
Wildfire band, earthquake risk, radon and flood studies for each place nearby.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Thornhill Woods | Low | $0.028 | 0% | Yes |
| Crossroads 4,525 · 1.2 km | Low | $0.028 | 0% | Yes |
| Dufferin Hill 7,910 · 1.7 km | Low | $0.028 | 0% | Yes |
| The Valleys of Thornhill 9,979 · 1.9 km | Low | $0.028 | 0% | Yes |
| Carrville Corners 13,004 · 2.7 km | Low | $0.028 | 0% | Yes |
| Beverley Glen 38,720 · 3.6 km | Low | $0.028 | 0% | Yes |
| Langstaff 8,147 · 3.9 km | Low | $0.034 | 0% | Yes |
Beverley Glen burns a little more than Thornhill Woods, 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 Thornhill Woods faces
What to do about the hazards Thornhill Woods 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
- Earthquakes are modelled. Shaking damage is modelled from the ground, the buildings and the odds of each quake, and published for whole subdivisions such as Thornhill Woods’.
- Wildfire counts one way. The wildfire figure is the share of land within 25 km of Thornhill Woods’ homes burned each year from 1986 to 2025, past fire rather than a forecast, and it can only lower Risk.
- Radon is a survey. About 14,000 homes were tested across Canada in 2009–2011, and the share over the guideline for Thornhill Woods 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 Thornhill Woods.
Questions about flooding and hazards in Thornhill Woods
Is radon a problem in Thornhill Woods?
In Health Canada’s survey, 0% of 95 homes tested in Thornhill Woods’ area were above 200 Bq/m³, though only a test tells you about one house.
How big is the earthquake risk in Thornhill Woods?
NRCan’s model expects shaking to cost buildings in Thornhill Woods $0.028 a year for every $1,000 of their value, on average over many years.
Is Thornhill Woods at risk of wildfire?
Hardly at all on record: 0% of the land within 25 km of Thornhill Woods since 1986, a low band, though small grass fires aren’t mapped.
How is Thornhill Woods’s Hazard risk Grade worked out?
Thornhill Woods’ Hazard risk grade is A, built on earthquakes and radon with a one-sided wildfire input.
Does Thornhill Woods flood?
There is flood mapping for Thornhill Woods on the national inventory, each study linked to its owner’s map, none of them graded.
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).