Photo: Pymouss · CC BY-SA 4.0A flood study covers Châteauguay: 2 on the national inventory, the newest from MRC Roussillon
Fire seldom reaches Châteauguay: since 1986, 0% of the land within 25 km has burned (0.001% a year). Seismic risk runs high: $0.20 of expected damage per $1,000 of buildings a year, the typical town $0.030. Châteauguay’s survey area, 8.2% over the radon guideline, is close to the typical town’s 6.6%. Hazard risk gives Châteauguay a grade of C−, from earthquakes and radon alone.
What stands out about Châteauguay’s hazards
For Châteauguay, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Châteauguay faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Hazard risk in Châteauguay: C−
For Châteauguay, Risk will be the average of earthquakes and radon, with wildfire added only if it makes the average worse.
Its place: #365 of 507 in Quebec and #2,337 of 2,589 Canadian towns.
How sure: Earthquake losses are a model’s expectation over many years, not a forecast for any one. The burned-area record misses fires under about 10 ha and most grass and farm fires.
Little of the land around Châteauguay has burned: 0.2% within 5 km, 0% within 25 km since 1986
Fires mapped since 1986 around where Châteauguay’s residents live, and the fuel next to their homes.
Around Châteauguay fire takes 0.001% of the land in a typical year, the typical Canadian town 0.000%, which is low.
Around Châteauguay the forest is thin or far off: 2% of the land within 5 km and 1.4% within 25 km is forest fuel.
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 Quebec · highest of 513
Châteauguay burns at 0.001% a year, 136th of 513 towns in Quebec; the leader, Mistissini, reaches 0.31%.
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.
Châteauguay 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.
Flooding around Châteauguay is mapped in 2 studies, the newest by MRC Roussillon
Flood studies whose area touches Châteauguay, from NRCan’s inventory, each linked to its owner.
The newest of 2 studies covering Châteauguay is MRC Roussillon’s, from 1996; open its map to see the zones.
| Study | By | Year | Status |
|---|---|---|---|
| Mercier | MRC Roussillon | 1996 | final |
| St-Louis-Varennes | Gouvernement du Québec | 1977 | final |
Towns with a flood study on file
Only 45% of towns in Quebec have a flood study, short of Canada’s 58%; Châteauguay is one of them.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
Flood mapping around Châteauguay has come in steps: 2 studies from the 1970s to the 1990s.
Study dates as the NRCan inventory lists them, one count per study touching Châteauguay.
Flood studies don’t enter the grade; they are listed so you can open the official map for Châteauguay.
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.
High seismic risk in Châteauguay: $0.20 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.
Châteauguay’s $0.20 is about 6.6 times the typical town’s $0.030: it sits in one of Canada’s more active seismic zones.
Shaking damage a year per $1,000 of building value
The typical town in Quebec expects $0.14 a year; Châteauguay expects $0.20, and La Pocatière $0.48.
NRCan seismic risk model (2022): mean yearly building loss per $1,000 of value; medians of towns of 2,500 people or more.
In the upper part of Canada’s range: 12% of its 2,611 towns expect more damage than Châteauguay.
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 Châteauguay 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).
Some radon around Châteauguay: 8.2% of area homes over the guideline
Health Canada’s survey of long-term home tests: the share above the 200 Bq/m³ guideline. · Measured across the Monteregie health region: radon tests
Châteauguay’s area, at 8.2%, is close to the 6.6% of the typical Canadian town.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Châteauguay’s area, at 8.2%, is close to the median in Quebec (8.2%).
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
Radon tops the guideline in a modest share of homes around Châteauguay, a band holding 37% of Canada’s 2,611 towns; 26% rank 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.
Neighbouring homes in Châteauguay can differ a lot; only a long-term test tells you about yours.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Where to get warnings in Châteauguay
Alerts for Châteauguay 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 Châteauguay 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 Châteauguay
The same four hazards for the places next door.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Châteauguay | Low | $0.20 | 8.2% | Yes |
| Kahnawake 11,142 · 4.5 km | Low | – | 8.2% | Yes |
| Mercier 16,036 · 5.1 km | Low | $0.19 | 8.2% | Yes |
| Léry 2,817 · 5.6 km | Low | $0.16 | 8.2% | Yes |
| Lachine-Ouest 15,315 · 9.3 km | Low | $0.20 | 6.8% | None listed |
| Dorval 21,062 · 9.4 km | Low | $0.19 | 6.8% | None listed |
| Saint-Isidore 2,889 · 9.6 km | Low | $0.20 | 8.2% | Yes |
None of the places around has more fire nearby than Châteauguay (low); Kahnawake comes closest (low).
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Châteauguay faces
Practical steps for Châteauguay’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.
- Drop, cover and hold on.
- Strap the water heater down.
- Keep 72 hours of supplies.
- Has it had a radon test?
- Check the address on the flood map.
- Are flood and wildfire insured?
- Is earthquake cover included?
What this data can and can’t tell you
- 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 Châteauguay.
- Earthquakes are modelled. The earthquake figure is an expected loss, not a forecast, worked out by NRCan for each census subdivision, Châteauguay’s included.
- Wildfire counts one way. Burned land within 25 km of where people live, averaged over 1986–2025 and checked for fuel near homes, is the measure; it looks back, not ahead, and only ever counts against Châteauguay.
- Radon is a survey. About 14,000 homes were tested across Canada in 2009–2011, and the share over the guideline for Châteauguay is its health region’s, the survey’s design unit.
Questions about flooding and hazards in Châteauguay
How is Châteauguay’s Hazard risk Grade worked out?
Châteauguay grades C− for hazard risk, from earthquakes and radon, with wildfire counted only where it lowers the grade.
Is radon a problem in Châteauguay?
8.2% of the 110 homes Health Canada tested around Châteauguay topped the guideline; your own house needs its own test.
Does Châteauguay flood?
There is flood mapping for Châteauguay on the national inventory, each study linked to its owner’s map, none of them graded.
How big is the earthquake risk in Châteauguay?
Expected earthquake damage in Châteauguay comes to $0.20 a year for each $1,000 that buildings are worth.
Is Châteauguay at risk of wildfire?
Not much by Canadian standards: Châteauguay’s band is low, with 0% of the land within 25 km burned since 1986 (last in 2025), so wildfire doesn’t change its grade.
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).