Photo: Gogerr · CC BY-SA 4.0Thorold is on Canada’s flood inventory: 9 listed, led by Niagara Peninsula Conservation Authority
For Thorold, wildfire history is close to nil: 0% of nearby land since 1986, 0.000% a year. Earthquakes add more: NRCan’s model puts building losses at $0.061 a year per $1,000 of value, against $0.030 for the typical town. In Health Canada’s survey, just 2% of homes tested in the area exceeded 200 Bq/m³ (6.6% typical). Hazard risk gives Thorold a grade of B+, from earthquakes and radon alone.
What stands out about Thorold’s hazards
For Thorold, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Thorold faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Thorold grades B+ for hazard risk
Seismic risk and radon set Thorold’s grade, wildfire can drag it down, and flood mapping stays out of it.
Its place: #470 of 866 in Ontario and #913 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 Thorold has burned: 0% within 5 km, 0% within 25 km since 1986
Past fire around Thorold’s homes, from the national burned-area record, with the fuel within 5 km.
In a typical year 0.000% of the land near Thorold burns; the typical Canadian town sees 0.000%, and both are low.
Around Thorold the forest is thin or far off: 1.6% of the land within 5 km and 0.9% 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 Ontario · highest of 871
Little or nothing burns around Thorold 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.
92% of Canada’s 2,610 towns are in the low band and 7.5% above it; Thorold is among the many where the yearly burn rate rounds to zero.
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.
Thorold is on the flood map inventory: 9 studies, latest by Niagara Peninsula Conservation Authority
What Canada’s Flood Map Inventory lists for Thorold: who studied flooding and where to see their maps.
The newest of 9 studies covering Thorold is Niagara Peninsula Conservation Authority’s, from 2018; open its map to see the zones.
| Study | By | Year | Status |
|---|---|---|---|
| Welland River | Niagara Peninsula Conservation Authority | 2018 | final |
| Singers Drain | Niagara Peninsula Conservation Authority | 2011 | final |
| Upper Twelve Mile Creek | Niagara Peninsula Conservation Authority | 2005 | final |
| City of St. Catherines | Niagara Peninsula Conservation Authority | 1995 | final |
| BeaverdamsCreek | Niagara Peninsula Conservation Authority | final | |
| ShrinersCreek | Niagara Peninsula Conservation Authority | final | |
| TenMileCreek | Niagara Peninsula Conservation Authority | final | |
| ThompsonCreek | Niagara Peninsula Conservation Authority | final |
1 more studies on the inventory touch Thorold.
Towns with a flood study on file
Its flood study puts Thorold with 69% of towns in Ontario; Canada’s share is 58%.
NRCan Canada Flood Map Inventory: a study footprint touching the town’s boundary; towns of 2,500 people or more.
The 2010s brought the most flood studies for Thorold (2 of 4), the first dating from the 1990s.
Study dates as the NRCan inventory lists them, one count per study touching Thorold.
Flood mapping is shown for Thorold to be opened and checked, never turned into a grade.
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.
Earthquakes cost buildings in Thorold $0.061 per $1,000 a year
Expected yearly building losses from earthquakes, from Natural Resources Canada’s model.
Roughly 2 times the typical $0.030: Thorold’s $0.061 marks real seismic exposure.
Shaking damage a year per $1,000 of building value
The typical town in Ontario expects $0.043 a year; Thorold expects $0.061, and Alexandria $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.
In the upper part of Canada’s range: 29% of its 2,611 towns expect more damage than Thorold.
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 Thorold 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).
Radon runs low around Thorold: 2% of tested homes over the guideline
Long-term radon tests in homes across the survey area, against Health Canada’s guideline. · Source area for radon tests: the Niagara Regional Area Health Unit
Thorold’s survey area reads 2% over the guideline, under the typical Canadian town’s 6.6%.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Thorold’s area, at 2%, is below the median in Ontario (4%), though 2% of its tests passed 600 Bq/m³.
Health Canada radon survey (2009–2011), by 2007 health region; medians of towns of 2,500 people or more.
Few tests over the guideline: Thorold 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 low area share in Thorold doesn’t clear a house, nor does a high one condemn it: test.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Where to get warnings in Thorold
Alerts for Thorold 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 Thorold 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)
Hazards in the places around Thorold
Wildfire band, earthquake risk, radon and flood studies for each place nearby.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Thorold | Low | $0.061 | 2% | Yes |
| St. Catharines 153,865 · 7.3 km | Low | $0.066 | 2% | Yes |
| Niagara Falls 113,983 · 9.5 km | Low | $0.066 | 2% | Yes |
| Pelham 19,980 · 10 km | Low | $0.055 | 2% | Yes |
| Welland 66,480 · 13 km | Low | $0.069 | 2% | Yes |
| Niagara-on-the-Lake 20,080 · 15 km | Low | $0.062 | 2% | Yes |
| Beamsville 28,356 · 18 km | Low | $0.058 | 2% | Yes |
Among its neighbours Thorold has the most fire on record (low); St. Catharines follows (low).
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Thorold faces
Practical steps for Thorold’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?
- 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. Radon figures pool the survey’s home tests by area: postal areas once their boundaries arrive, the 2007 health region around Thorold until then.
- 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 Thorold.
- Earthquakes are modelled. The earthquake figure is an expected loss, not a forecast, worked out by NRCan for each census subdivision, Thorold’s included.
- Flood studies aren’t flood zones. Flood studies cover areas of every size, which is why the page lists them for Thorold without grading them.
Questions about flooding and hazards in Thorold
Is radon a problem in Thorold?
The area’s survey found 2% of 100 tested homes above Health Canada’s guideline, so a three-month test is worth doing in Thorold.
Does Thorold flood?
A flood study covers Thorold on Canada’s Flood Map Inventory; open the owner’s map to check a street, since flood isn’t graded.
Is Thorold at risk of wildfire?
No meaningful wildfire history near Thorold: 0% of nearby land since 1986, band low.
How is Thorold’s Hazard risk Grade worked out?
Thorold’s Hazard risk grade is B+, built on earthquakes and radon with a one-sided wildfire input.
How big is the earthquake risk in Thorold?
In NRCan’s seismic model, Thorold’s buildings lose $0.061 per $1,000 of value in an average year.
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).