Hazards in Guernsey: wildfire low, radon over the guideline in 5% of tested homes
No wildfire is mapped within 25 km of Guernsey’s homes since 1986 (0% of the land, 0.000% a year). For earthquakes Guernsey is middling, $0.044 a year per $1,000 against $0.030 for the typical town. Hazard risk gives Guernsey a grade of B+, from earthquakes and radon alone.
What stands out about Guernsey’s hazards
For Guernsey, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Guernsey faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Guernsey grades B+ for hazard risk
Risk averages earthquakes and radon; wildfire joins only where it pulls the average down, so a town like Guernsey with little fire nearby would get no credit for it.
Its place: #494 of 866 in Ontario and #1,255 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.
Little of the land around Guernsey has burned: 0% within 5 km, 0% within 25 km since 1986
Fires mapped since 1986 around where Guernsey’s residents live, and the fuel next to their homes.
In a typical year 0.000% of the land near Guernsey burns; the typical Canadian town sees 0.000%, and both are low.
Only 0.5% of the land within 25 km of Guernsey is forest fuel, and 0.2% close in.
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
Little or nothing burns around Guernsey in a typical year; 638 of the 871 towns in Ontario share that, and Sioux Lookout leads 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.
Only 7.5% of Canada’s 2,610 towns are above the low band, which holds 92%; Guernsey, at a rounded zero, is far from them.
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 Guernsey
Flood studies whose area touches Guernsey, from NRCan’s inventory, each linked to its owner.
There is no study for Guernsey on the national flood inventory, which is far from complete.
Towns with a flood study on file
69% of towns in Ontario have a flood study, more than Canada’s 58%; Guernsey is not yet one of them.
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 Guernsey 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.”
Expected shaking damage in Guernsey: $0.044 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.
With $0.044 of shaking damage a year per $1,000, Guernsey is about even with the typical $0.030 (1.5 times).
Shaking damage a year per $1,000 of building value
About level with the typical town in Ontario: Guernsey’s $0.044 against $0.043; Alexandria reaches $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.
32% of Canada’s 2,611 towns expect more shaking damage than Guernsey, which places it in the upper third.
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).
For Guernsey the model prices shaking damage to buildings, nothing more.
Natural Resources Canada, Canada’s Seismic Risk Model (2022), by census subdivision (2016 boundaries; a few 2021 subdivisions take their residents’ mean). · Not measured by town: earthquake risk (the city of Hamilton)
Radon about average around Guernsey: 5% over the guideline
Health Canada’s survey of long-term home tests: the share above the 200 Bq/m³ guideline.
Near the middle for radon: Guernsey’s area 5%, the typical Canadian town 6.6%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Radon runs higher around Guernsey than in most towns in Ontario: 5% against 4%.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
A middling share of high tests puts Guernsey with 37% of Canada’s 2,611 towns, below 26% of them.
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, Guernsey’s included, whatever the area’s figure.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011). · Radon tests: the City of Hamilton Health Unit
Where to get warnings in Guernsey
Alerts for Guernsey 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 Guernsey 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 Guernsey’s neighbours compare on hazards
The same four hazards for the places next door.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Guernsey | Low | $0.044 | 5% | None listed |
| Westmeria 2,646 · 0.7 km | Low | $0.044 | 5% | None listed |
| Poplar Park 3,031 · 1.2 km | Low | $0.044 | 5% | None listed |
| Highway Valley 4,469 · 1.4 km | Low | $0.044 | 5% | None listed |
| Lakeshore 3,127 · 1.8 km | Low | $0.044 | 5% | None listed |
| Eastdale 2,703 · 1.8 km | Low | $0.044 | 5% | None listed |
| Riverdale East 3,416 · 2.5 km | Low | $0.044 | 5% | None listed |
Guernsey’s low band tops its neighbours; Westmeria is next (low).
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Guernsey faces
What to do about the hazards Guernsey 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
- Earthquakes are modelled. Seismic risk is NRCan’s model of yearly building losses from shaking, averaged over many years and given for Guernsey’s census subdivision (a neighbourhood shows its city’s).
- 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 Guernsey 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 Guernsey floods.
- Wildfire counts one way. For Guernsey, wildfire means how much nearby land burned in the past forty years, a one-way input that can pull Risk down and nothing more.
Questions about flooding and hazards in Guernsey
How is Guernsey’s Hazard risk Grade worked out?
Guernsey grades B+ for hazard risk, from earthquakes and radon, with wildfire counted only where it lowers the grade.
Is Guernsey at risk of wildfire?
Very little by the national record: Guernsey’s band is low, with 0% of the land within 25 km burned since 1986, so wildfire doesn’t change its grade.
How big is the earthquake risk in Guernsey?
About $0.044 a year per $1,000 of building value, NRCan’s long-run expectation for Guernsey.
Is radon a problem in Guernsey?
Around Guernsey, 100 survey homes were tested and 5% came in over 200 Bq/m³, a guide to the area, not to any one home.
Does Guernsey flood?
With 0 studies on the inventory, Guernsey’s flood risk is unmapped nationally; check with the municipality before buying.
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).