Photo: Carlosgabriel11 · CC BY-SA 3.0Unionville faces fewer hazards than 88% of Canadian towns
Wildfire barely registers for Unionville, at 0% of the land within 25 km since 1986 (0.001% a year). Seismic risk in Unionville sits near the middle: $0.034 of expected damage per $1,000 of buildings a year, the typical town $0.030. Fewer homes than usual carry radon here, 0% over the guideline where the typical town has 6.6%. Hazard risk gives Unionville a grade of A; its wildfire band pulls it down.
What stands out about Unionville’s hazards
For Unionville, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Unionville faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Hazard risk in Unionville: A
Earthquake risk and radon make Unionville’s grade; wildfire can only lower it, never raise it, and flood studies are listed but not scored.
Its place: #165 of 866 in Ontario and #484 of 2,589 Canadian towns.
How sure: The seismic figure is a long-run average from NRCan’s model, not a prediction. The burned-area record misses fires under about 10 ha and most grass and farm fires.
Few fires near Unionville: 0% within 5 km, 0% within 25 km
Fires mapped since 1986 around where Unionville’s residents live, and the fuel next to their homes.
At 0.001% of the land a year, Unionville’s burn rate is in the low band; the typical Canadian town sees 0.000%.
No fire has burned within 5 km of Unionville’s homes since 1986; the nearest burn is 12 km away.
Forest fuel rises from 0.7% within 5 km of Unionville to 6.7% within 25 km: the fuel lies away from homes.
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
In the top quarter in Ontario: Unionville ranks 83rd of 871 at 0.001% a year, with Sioux Lookout first 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.
Unionville is in the low band with 92% of Canada’s 2,610 towns; 7.5% sit in moderate or higher.
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.
2 flood studies cover Unionville, the newest from Toronto Regional Conservation Authority
Flood studies whose area touches Unionville, from NRCan’s inventory, each linked to its owner.
2 studies on the inventory touch Unionville, the newest Toronto Regional Conservation Authority’s from 2021, and their areas can be large, so they say maps exist, not that the town floods.
| Study | By | Year | Status |
|---|---|---|---|
| Toronto Floodline Consolidation | Toronto Regional Conservation Authority | 2021 | final |
| Unionville Special Policy Area | Toronto and Region Conservation Authority | 2019 | final |
Towns with a flood study on file
69% of towns in Ontario have a flood study, more than Canada’s 58%; Unionville has one too.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
The 2 studies touching Unionville are spread over time, from the 2010s to the 2020s.
Study dates as the NRCan inventory lists them, one count per study touching Unionville.
Flood studies don’t enter the grade; they are listed so you can open the official map for Unionville.
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 Unionville: $0.034 a year per $1,000
NRCan’s seismic risk model: the damage shaking is expected to do to buildings each year, on average over many years.
At $0.034 per $1,000, Unionville’s earthquake risk is about the typical Canadian town’s ($0.030; 1.1 times).
Figures for earthquake risk are published for the city of Markham as a whole, not for Unionville alone.
Shaking damage a year per $1,000 of building value
The typical town in Ontario expects $0.043 a year in shaking damage; Unionville expects less, $0.034, and Alexandria the most, $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.
Neither high nor low for Canada: 46% of the 2,611 towns expect more damage than Unionville.
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).
What a quake does after the shaking, fire, landslides, tsunami, falls outside NRCan’s figure for Unionville.
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 Unionville: 0% of tested homes over the guideline
Health Canada’s survey of long-term home tests: the share above the 200 Bq/m³ guideline.
Radon runs below the typical Canadian town (6.6%) in Unionville’s area, at 0%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Unionville’s area, at 0%, is below the median in Ontario (4%).
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
Few tests over the guideline: Unionville shares the bottom band with 37% of Canada’s 2,611 towns, below the other 63%.
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.
Health Canada advises testing every home, Unionville’s included, whatever the area’s figure.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011). · Data for radon tests covers the York Regional Health Unit
Where to get warnings in Unionville
Alerts for Unionville come from Environment and Climate Change Canada and, for emergencies, Alert Ready.
| 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. |
Fire danger and active fires near Unionville are mapped daily by the Canadian Wildland Fire Information System; evacuation orders come from the municipality or province.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
How Unionville’s neighbours compare on hazards
The same four hazards for the places next door.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Unionville | Low | $0.034 | 0% | Yes |
| Cachet 6,361 · 2.2 km | Low | $0.034 | 0% | Yes |
| Quantztown 13,146 · 2.3 km | Low | $0.034 | 0% | Yes |
| Brown's Corners 7,228 · 2.4 km | Low | $0.034 | 0% | Yes |
| Berczy Village 22,149 · 2.5 km | Low | $0.034 | 0% | Yes |
| Buttonville 15,001 · 3.0 km | Low | $0.034 | 0% | Yes |
| Hagerman's Corners 43,555 · 3.4 km | Low | $0.034 | 0% | Yes |
None of the places around has more fire nearby than Unionville (low); Cachet comes closest (low).
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Unionville faces
Practical steps for Unionville’s hazards, most pressing first.
- 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. Radon figures pool the survey’s home tests by area: postal areas once their boundaries arrive, the 2007 health region around Unionville until then.
- Wildfire counts one way. For Unionville, wildfire means how much nearby land burned in the past forty years, a one-way input that can pull Risk down and nothing more.
- Earthquakes are modelled. Seismic risk is NRCan’s model of yearly building losses from shaking, averaged over many years and given for Unionville’s census subdivision (a neighbourhood shows its city’s).
- Flood studies aren’t flood zones. Flood studies cover areas of every size, which is why the page lists them for Unionville without grading them.
Questions about flooding and hazards in Unionville
Is Unionville at risk of wildfire?
Not much by Canadian standards: Unionville’s band is low, with 0% of the land within 25 km burned since 1986 (last in 2001), so wildfire doesn’t change its grade.
How is Unionville’s Hazard risk Grade worked out?
Unionville grades A for hazard risk, from earthquakes and radon, with wildfire counted only where it lowers the grade.
Does Unionville flood?
A flood study covers Unionville on Canada’s Flood Map Inventory; open the owner’s map to check a street, since flood isn’t graded.
How big is the earthquake risk in Unionville?
About $0.034 a year per $1,000 of building value, NRCan’s long-run expectation for Unionville.
Is radon a problem in Unionville?
0% of the 95 homes Health Canada tested around Unionville topped the guideline; your own house needs its own test.
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).