Photo: Michael Gil · CC BY 2.0Hazard risk in Alliston is lower than in 92% of Canadian towns
Around Alliston, wildfire is practically absent from the record: 0% within 25 km since 1986, 0.001% a year. NRCan expects $0.020 of shaking damage a year per $1,000 of buildings in Alliston, near the typical $0.030. Radon is lower than usual: 0.9% of tested homes in the survey area topped the guideline, against 6.6% for the typical town. Alliston grades A for hazard risk, with wildfire counted against it.
What stands out about Alliston’s hazards
Four national sources, each read for Alliston: earthquakes, radon, past fires and flood studies.
What Alliston faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Alliston grades A for hazard risk
For Alliston, Risk will be the average of earthquakes and radon, with wildfire added only if it makes the average worse.
Its place: #30 of 866 in Ontario and #282 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.
Little of the land around Alliston has burned: 0% within 5 km, 0% within 25 km since 1986
Past fire around Alliston’s homes, from the national burned-area record, with the fuel within 5 km.
Low by Canadian standards: 0.001% of the land a year around Alliston, 0.000% for the typical Canadian town.
Since 1986 the nearest fire to Alliston’s homes came within 19 km, never inside 5 km.
Forest fuel covers 5.8% of the land close to Alliston and 13% across 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
Sioux Lookout burns fastest in Ontario at 0.16% a year; Alliston, at 0.001%, ranks 83rd of 871.
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.
Beside 2,610 Canadian towns, Alliston reads low, with 92% of them; only 7.5% rank 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.
No flood study is listed for Alliston
What Canada’s Flood Map Inventory lists for Alliston: who studied flooding and where to see their maps.
There is no study for Alliston on the national flood inventory, which is far from complete.
Towns with a flood study on file
Alliston has no flood study on file, though 69% of towns in Ontario do (Canada: 58%).
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
Listed, not scored: a flood study proves a map exists, not that Alliston floods.
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.”
Ordinary seismic risk in Alliston: $0.020 per $1,000 of buildings a year
Expected yearly building losses from earthquakes, from Natural Resources Canada’s model.
0.7 times the typical $0.030: Alliston’s $0.020 is ordinary.
Shaking damage a year per $1,000 of building value
Below the middle in Ontario: Alliston’s $0.020 against a median of $0.043; Alexandria has $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: 64% of the 2,611 towns expect more damage than Alliston.
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 Alliston’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).
0.9% of homes tested around Alliston are over the radon guideline
Long-term radon tests in homes across the survey area, against Health Canada’s guideline.
Alliston’s area, at 0.9%, is below the 6.6% of the typical Canadian town, though any one home can still be high.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
The median in Ontario is 4% over 200 Bq/m³; around Alliston it is 0.9%.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
Few tests over the guideline: Alliston 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.
A survey sample isn’t a map: any home in Alliston can be high, and a three-month test is the only way to know.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011). · Radon tests published for the Simcoe Muskoka District Health Unit, not by town
Weather and fire alerts for Alliston
Alerts for Alliston 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. |
Evacuation orders for Alliston come from the municipality or the province, while CWFIS maps fire danger every day.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
How Alliston’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 |
|---|---|---|---|---|
| Alliston | Low | $0.020 | 0.9% | None listed |
| Adjala-Tosorontio 11,948 · 14 km | Low | $0.017 | 0.9% | Yes |
| Bradford 51,346 · 18 km | Low | $0.019 | 0.9% | None listed |
Bradford (low) has the heaviest fire record of Alliston’s neighbours, and Alliston (low) matches or beats it.
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Alliston faces
Practical steps for Alliston’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?
- Ask the municipality for flood maps.
- 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 Alliston is its health region’s, the survey’s design unit.
- 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 Alliston’s.
- 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 Alliston.
- Wildfire counts one way. The wildfire figure is the share of land within 25 km of Alliston’s homes burned each year from 1986 to 2025, past fire rather than a forecast, and it can only lower Risk.
Questions about flooding and hazards in Alliston
Is radon a problem in Alliston?
0.9% of the 109 homes Health Canada tested around Alliston topped the guideline; your own house needs its own test.
Is Alliston at risk of wildfire?
Not much by Canadian standards: Alliston’s band is low, with 0% of the land within 25 km burned since 1986 (last in 2006), so wildfire doesn’t change its grade.
Does Alliston flood?
No study on Canada’s Flood Map Inventory covers Alliston (0), which doesn’t mean it has never been mapped, so ask the municipality.
How is Alliston’s Hazard risk Grade worked out?
Hazard risk gives Alliston A, weighing earthquakes and radon and counting wildfire only against it.
How big is the earthquake risk in Alliston?
NRCan’s model expects shaking to cost buildings in Alliston $0.020 a year for every $1,000 of their value, on average over many years.
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).