Photo: Andre Carrotflower · CC BY-SA 4.0Few places are as safe from hazards as Thessalon: it beats 86% of Canadian towns
For Thessalon, wildfire history is close to nil: 0% of nearby land since 1986, 0.001% a year. Seismic risk runs low: $0.005 of expected damage per $1,000 of buildings a year, the typical town $0.030. About as many homes carry radon around Thessalon as elsewhere, 8.6% over the guideline where the typical town has 6.6%. Hazard risk gives Thessalon a grade of A; its wildfire band pulls it down.
What stands out about Thessalon’s hazards
Four national sources, each read for Thessalon: earthquakes, radon, past fires and flood studies.
What Thessalon faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Thessalon grades A for hazard risk
Risk averages earthquakes and radon; wildfire joins only where it pulls the average down, so a town like Thessalon with little fire nearby would get no credit for it.
How sure: The seismic figure is a long-run average from NRCan’s model, not a prediction. Small fires and grass fires are largely missing from the national burned-area record.
Little of the land around Thessalon has burned: 0% within 5 km, 0% within 25 km since 1986
Past fire around Thessalon’s homes, from the national burned-area record, with the fuel within 5 km.
In a typical year 0.001% of the land near Thessalon burns; the typical Canadian town sees 0.000%, and both are low.
Since 1986 the nearest fire to Thessalon’s homes came within 14 km, never inside 5 km.
The ring nearest Thessalon is the most wooded: 31% forest fuel within 5 km against 25% 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
Thessalon ranks 83rd of the 872 towns in Ontario for burn rate, at 0.001% a year; Sioux Lookout leads with 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.
Some fire is mapped around Thessalon, but not enough to leave the low band, where 92% of Canada’s 2,610 towns are; 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.
The Corporation of the Municipality of Huron Shores has mapped flooding for Thessalon (1 study)
What Canada’s Flood Map Inventory lists for Thessalon: who studied flooding and where to see their maps.
The Corporation of the Municipality of Huron Shores studied flooding in an area that includes Thessalon (2024); open its map to see which streets lie in a flood zone.
| Study | By | Year | Status |
|---|---|---|---|
| Huron Shores Floodplain Mapping Study | The Corporation of the Municipality of Huron Shores | 2024 | final |
Towns with a flood study on file
Thessalon 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.
Flood studies don’t enter the grade; they are listed so you can open the official map for Thessalon.
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.
Little shaking expected in Thessalon: $0.005 a year per $1,000
Expected yearly building losses from earthquakes, from Natural Resources Canada’s model.
Thessalon’s $0.005 is a fraction of the typical town’s $0.030 (0.2 times as much): quiet ground by Canadian standards.
Shaking damage a year per $1,000 of building value
The typical town in Ontario expects $0.043 a year in shaking damage; Thessalon expects less, $0.005, 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.
At the bottom of Canada’s range, Thessalon has 96% of the 2,611 towns above it.
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 Thessalon’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 about average around Thessalon: 8.6% over the guideline
Long-term radon tests in homes across the survey area, against Health Canada’s guideline. · Measured across the The District of Algoma Health Unit: radon tests
Around Thessalon, 8.6% of tested homes topped the guideline, near the typical Canadian town’s 6.6%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Around Thessalon, 8.6% of tests were over 200 Bq/m³ and 1.1% over 600, against a median of 4% in Ontario.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
Thessalon is in the 5–10% band with 37% of Canada’s 2,611 towns; 26% have 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.
The survey sampled homes around Thessalon; it can’t tell you your basement’s level.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Weather and fire alerts for Thessalon
Alerts for Thessalon 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 Thessalon 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)
Hazards in the places around Thessalon
Wildfire band, earthquake risk, radon and flood studies for each place nearby.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Thessalon | Low | $0.005 | 8.6% | Yes |
| Huron Shores 2,030 · 16 km | Low | $0.006 | 8.6% | Yes |
None of the places around has more fire nearby than Thessalon (low); Huron Shores comes closest (low).
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Thessalon faces
What to do about the hazards Thessalon 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. The radon share comes from about 14,000 long-term home tests in 2009–2011, pooled for now by the 2007 health region Thessalon sits in.
- Flood studies aren’t flood zones. A study’s area can be a whole watershed or province, so being on the inventory says a map exists, not that a home in Thessalon floods.
- Wildfire counts one way. The wildfire figure is the share of land within 25 km of Thessalon’s homes burned each year from 1986 to 2025, past fire rather than a forecast, and it can only lower Risk.
- 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 Thessalon’s.
Questions about flooding and hazards in Thessalon
Is Thessalon at risk of wildfire?
Less than most of Canada: 0% of the land within 25 km of Thessalon has burned since 1986, the last in 1999, a low band that leaves Risk alone.
Is radon a problem in Thessalon?
In Health Canada’s survey, 8.6% of 93 homes tested in Thessalon’s area were above 200 Bq/m³, though only a test tells you about one house.
How big is the earthquake risk in Thessalon?
NRCan’s model expects shaking to cost buildings in Thessalon $0.005 a year for every $1,000 of their value, on average over many years.
How is Thessalon’s Hazard risk Grade worked out?
Thessalon grades A for hazard risk, from earthquakes and radon, with wildfire counted only where it lowers the grade.
Does Thessalon flood?
Thessalon’s area has been studied for flooding, and the owner’s map shows which streets lie in a zone; the grade leaves flood out.
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).