Photo: Ryan Hodnett · CC BY-SA 4.0A flood study covers Guelph: 1 on the national inventory, the newest from Grand River Conservation Authority
The burned-area map is nearly blank around Guelph, 0% within 25 km since 1986, 0.000% a year. Seismic risk in Guelph sits near the middle: $0.024 of expected damage per $1,000 of buildings a year, the typical town $0.030. Radon is higher than usual: 11% of tested homes in the survey area topped the guideline, against 6.6% for the typical town. Guelph grades C+ for hazard risk; wildfire is low here, so it earns no credit.
What stands out about Guelph’s hazards
For Guelph, from NRCan’s seismic model, Health Canada’s radon survey, the national burned-area record and the flood map inventory.
What Guelph faces
Each hazard against its own yardstick; meters run from low to high on that yardstick.
Wildfire
Earthquakes
Radon
Flood study
Hazard risk in Guelph: C+
Seismic risk and radon set Guelph’s grade, wildfire can drag it down, and flood mapping stays out of it.
Its place: #669 of 866 in Ontario and #1,769 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.
Few fires near Guelph: 0% within 5 km, 0% within 25 km
Fires mapped since 1986 around where Guelph’s residents live, and the fuel next to their homes.
Guelph burns at 0.000% a year, low against 0.000% for the typical Canadian town.
10% of the land within 5 km of Guelph is forest fuel, close to the 9.1% 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
Among the 871 towns in Ontario, Sioux Lookout burns fastest (0.16% a year); Guelph is with the 638 near zero.
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.
Measured against 2,610 towns, Guelph is in the largest group, low (92%), and at its floor, while 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.
A flood study covers Guelph, from Grand River Conservation Authority: 1 on the inventory
Flood studies whose area touches Guelph, from NRCan’s inventory, each linked to its owner.
Grand River Conservation Authority holds the flood mapping that covers Guelph (2018), linked below.
| Study | By | Year | Status |
|---|---|---|---|
| Grand River Regulatory Floodplain | Grand River Conservation Authority | 2018 | final |
Towns with a flood study on file
Guelph 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 mapping is shown for Guelph 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 Guelph $0.024 per $1,000 a year
NRCan’s seismic risk model: the damage shaking is expected to do to buildings each year, on average over many years.
0.8 times the typical $0.030: Guelph’s $0.024 is ordinary.
Shaking damage a year per $1,000 of building value
Below the middle in Ontario: Guelph’s $0.024 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.
Guelph sits mid-range among Canada’s 2,611 towns: 54% expect more shaking damage.
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 Guelph 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).
Test for radon in Guelph: 11% of area homes were over the guideline
Health Canada’s survey of long-term home tests: the share above the 200 Bq/m³ guideline.
A higher share than most: 11% of tested homes around Guelph, the typical Canadian town 6.6%. For radon tests, the only official count covers all of the Wellington-Dufferin-Guelph Health Unit, Guelph included.
Tested homes over 200 Bq/m³
Over 600 Bq/m³
Around Guelph, 11% of tests were over 200 Bq/m³ and 2% 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.
4.6% of Canada’s 2,611 towns have a higher share of homes over 200 Bq/m³ than Guelph, in the 10–20% band with 22%.
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, Guelph’s included, whatever the area’s figure.
Health Canada, Cross-Canada Survey of Radon Concentrations in Homes (2009–2011).
Where to get warnings in Guelph
Alerts for Guelph 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 Guelph 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 Guelph
The same four hazards for the places next door.
| Town | Wildfire | Quake $/1,000 | Radon | Flood study |
|---|---|---|---|---|
| Guelph | Low | $0.024 | 11% | Yes |
| Rockwood 14,870 · 5.3 km | Low | $0.022 | 11% | Yes |
| Puslinch 8,577 · 9.9 km | Low | $0.026 | 11% | Yes |
| Grand River South 10,723 · 17 km | Low | $0.022 | 4% | Yes |
| Grand River North 3,823 · 18 km | Low | $0.022 | 4% | Yes |
| Cambridge 165,354 · 18 km | Low | $0.024 | 4% | Yes |
| Idlewood 5,005 · 18 km | Low | $0.022 | 4% | Yes |
None of the places around has more fire nearby than Guelph (low); Rockwood comes closest (low).
Radon is the survey area’s figure, so neighbours in one area share it.
Get ready for what Guelph faces
Practical steps for Guelph’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
- Earthquakes are modelled. Seismic risk is NRCan’s model of yearly building losses from shaking, averaged over many years and given for Guelph’s census subdivision (a neighbourhood shows its city’s).
- Flood studies aren’t flood zones. The flood inventory points to maps; it is incomplete and not the official source, so ask the municipality about any street in Guelph.
- Wildfire counts one way. For Guelph, wildfire means how much nearby land burned in the past forty years, a one-way input that can pull Risk down and nothing more.
- Radon is a survey. Health Canada’s survey tested some 14,000 homes over three months; until postal-area boundaries are loaded, Guelph takes its 2007 health region’s share.
Questions about flooding and hazards in Guelph
Is Guelph at risk of wildfire?
Hardly at all on record: 0% of the land within 25 km of Guelph since 1986, a low band, though small grass fires aren’t mapped.
Does Guelph flood?
The inventory lists a study touching Guelph; whether a given street floods is on that map, not in the grade.
How is Guelph’s Hazard risk Grade worked out?
Hazard risk gives Guelph C+, weighing earthquakes and radon and counting wildfire only against it.
How big is the earthquake risk in Guelph?
Expected earthquake damage in Guelph comes to $0.024 a year for each $1,000 that buildings are worth.
Is radon a problem in Guelph?
The area’s survey found 11% of 99 tested homes above Health Canada’s guideline, so a three-month test is worth doing in Guelph.
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).