Photo: JustSomePics · CC BY-SA 3.0Chesley’s hazards at a glance: a low wildfire record and 11% of area homes over the radon guideline
Fire has left almost no mark near Chesley: 0% of the land within 25 km since 1986, 0.000% a year. Seismic risk runs low: $0.014 of expected damage per $1,000 of buildings a year, the typical town $0.030. Hazard risk gives Chesley a grade of B, from earthquakes and radon alone.
What stands out about Chesley’s hazards
Four national sources, each read for Chesley: earthquakes, radon, past fires and flood studies.
What Chesley faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Hazard risk in Chesley: B
Risk averages earthquakes and radon; wildfire joins only where it pulls the average down, so a town like Chesley with little fire nearby would get no credit for it.
Its place: #628 of 866 in Ontario and #1,441 of 2,589 Canadian towns.
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 Chesley has burned: 0% within 5 km, 0% within 25 km since 1986
Fires mapped since 1986 around where Chesley’s residents live, and the fuel next to their homes.
At 0.000% of the land a year, Chesley’s burn rate is in the low band; the typical Canadian town sees 0.000%.
The forest starts beyond town: 1.7% of the land within 5 km of Chesley’s homes is forest fuel, against 11% 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
Of the 871 towns in Ontario, 638 have a burn rate that rounds to zero, Chesley among them; Sioux Lookout leads at 0.16% a year.
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.
The low band holds 92% of Canada’s 2,610 towns, and Chesley sits at its very bottom; only 7.5% are above it.
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 flood map inventory lists nothing for Chesley
Flood studies whose area touches Chesley, from NRCan’s inventory, each linked to its owner.
Nationally, Chesley has no listed flood study; the municipality is the place to ask.
Towns with a flood study on file
Missing from a well-mapped province: Chesley has no study, where 69% of towns in Ontario have one against 58% nationally.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
Nothing here counts toward Risk; the studies are pointers to the maps their owners keep for Chesley.
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.”
Low seismic risk in Chesley: $0.014 per $1,000 of buildings a year
NRCan’s seismic risk model: the damage shaking is expected to do to buildings each year, on average over many years.
0.5 times the typical $0.030: Chesley’s $0.014 is low for Canada.
Shaking damage a year per $1,000 of building value
Below the middle in Ontario: Chesley’s $0.014 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.
Earthquakes cost less around Chesley than in 73% of Canada’s 2,611 towns.
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 Chesley’s 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).
Radon runs high around Chesley: 11% of tested homes over the guideline
Health Canada’s survey of long-term home tests: the share above the 200 Bq/m³ guideline.
Chesley’s area, at 11%, is above the 6.6% of the typical Canadian town, so testing is worth more here than most places.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
More homes top the guideline around Chesley (11%) than in the typical town in Ontario (4%); 1% went over 600.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
More high tests than most: Chesley sits in a band that only 22% of Canada’s 2,611 towns share, with 4.6% above.
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 Chesley; it can’t tell you your basement’s level.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011). · Radon tests: the Grey Bruce Health Unit
Weather and fire alerts for Chesley
Environment and Climate Change Canada issues the weather alerts for Chesley; 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 Chesley, and listen to local authorities for orders.
Weather alerts (ECCC) · Alert Ready · Fire danger and active fires (CWFIS)
Get ready for what Chesley faces
What to do about the hazards Chesley 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?
- Ask the municipality for flood maps.
- Are flood and wildfire insured?
What this data can and can’t tell you
- Flood studies aren’t flood zones. Flood studies cover areas of every size, which is why the page lists them for Chesley without grading them.
- Wildfire counts one way. Wildfire is read from the national burned-area record around Chesley’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; Chesley’s figure is its subdivision’s.
- 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 Chesley until then.
Questions about flooding and hazards in Chesley
Is radon a problem in Chesley?
Around Chesley, 98 survey homes were tested and 11% came in over 200 Bq/m³, a guide to the area, not to any one home.
Is Chesley at risk of wildfire?
The burned-area record shows next to nothing around Chesley (0% within 25 km since 1986), so its band is low.
Does Chesley flood?
With 0 studies on the inventory, Chesley’s flood risk is unmapped nationally; check with the municipality before buying.
How is Chesley’s Hazard risk Grade worked out?
Chesley’s Hazard risk grade is B, built on earthquakes and radon with a one-sided wildfire input.
How big is the earthquake risk in Chesley?
Expected earthquake damage in Chesley comes to $0.014 a year for each $1,000 that buildings are worth.
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).