In January 1998, freezing rain fell on eastern Ontario, southern Quebec and parts of the Maritimes in three waves over about five days. In the worst areas, around 100 mm of ice built up on everything. Steel transmission towers crumpled under the weight, and more than four million people lost power in the middle of winter, some for weeks. Freezing rain is common in Canada; what made this a disaster was how much fell, for how long, on a region full of people who depended on the power grid. Understanding that difference is the key to reducing the damage the next time.
Hazard, disaster and risk
A natural hazard is a natural event that could harm people or property, such as an earthquake, flood or wildfire. It becomes a disaster when it seriously disrupts a community, causing deaths, injuries or damage beyond what the community can handle on its own. Whether that happens depends on vulnerability: how exposed people are and how well they can prepare, cope and recover. A useful way to think about it is risk = hazard × vulnerability. A powerful tornado over an empty field is a hazard with low risk; the same tornado over a town is high risk. Reducing either part reduces the risk.
| Hazard | Where it is most common | A Canadian example |
|---|---|---|
| Earthquake | BC coast and Yukon; the Ottawa–Montréal area; the St. Lawrence valley | Haida Gwaii, August 22, 1949 (magnitude 8.1), the largest recorded in Canada |
| Landslide | Mountain slopes of the Cordillera; unstable clay along the Ottawa and St. Lawrence valleys | Frank Slide, Alberta, April 29, 1903: rock from Turtle Mountain buried part of the town, killing about 70 to 90 people |
| Tornado | Southern Ontario, the Prairies and southern Quebec, mostly in late spring and summer | Elie, Manitoba, June 22, 2007: Canada's only confirmed F5 tornado; Ottawa–Gatineau, September 21, 2018 (EF3) |
| Hurricane or post-tropical storm | Atlantic Canada, from June to November | Fiona, September 24, 2022: the costliest extreme weather event on record in Atlantic Canada |
| Ice storm | Eastern Ontario, southern Quebec, the Maritimes | January 5 to 10, 1998: over four million people lost power |
| Flood | River valleys and low coasts across Canada, often in spring snowmelt | Red River, Manitoba, 1997; southern BC atmospheric river, November 2021 |
| Wildfire | Boreal and western forests, from spring to fall | Fort McMurray, May 2016: about 88,000 people evacuated; 2023: Canada's worst season on record |
| Heat wave | Anywhere, most dangerous in cities and normally cool places | BC heat dome, late June 2021: Lytton reached 49.6 °C, Canada's highest temperature on record |
Patterns and trends
- Spatial patterns: earthquakes cluster along the BC coast near plate boundaries; tornadoes cluster where warm, humid air meets cooler, drier air, in southern Ontario and on the Prairies; hurricanes reach the Atlantic provinces; wildfires burn mainly in the boreal and western forests.
- Seasonal patterns: spring floods from snowmelt and ice jams, summer tornadoes and heat waves, late-summer and fall hurricanes, winter ice storms and blizzards.
- Trends in severity: Canada's 2023 wildfire season burned roughly 15 to 18 million hectares (agencies' counts differ), about double the previous record of about 7.6 million hectares set in 1989, and 2025 became the second-worst season on record. Insured losses from severe weather have risen sharply since the 1990s.
- Why trends are rising: a warming climate makes heat waves, wildfires and heavy downpours more likely, while more people and more expensive buildings sit in harm's way.
Reducing risk: before, during and after
| Stage | What it means | Canadian examples |
|---|---|---|
| Mitigation (prevention) | Lower the hazard or the vulnerability before anything happens | Earthquake-resistant building codes in BC and the Ottawa–Montréal area; floodplain mapping and no-build zones; the Red River Floodway around Winnipeg (built 1962–1968, expanded after the 1997 flood); FireSmart clearing around homes |
| Preparedness | Plan and practise so people are ready | Community emergency plans; a 72-hour home emergency kit; Alert Ready warnings on phones, radio and TV; earthquake drills |
| Response | Act during and right after the event to save lives | Evacuations, firefighting, search and rescue, warming centres, calling in the Canadian Armed Forces |
| Recovery | Rebuild and learn lessons | Disaster assistance, rebuilding stronger or moving out of high-risk areas, reviewing what went wrong |
Human choices can make hazards worse. Paving land means rain runs off instead of soaking in, raising flood peaks. Building on floodplains or at the edge of forests puts people in harm's way. Draining wetlands removes natural sponges: Sumas Lake in BC's Fraser Valley was drained between 1920 and 1924 to create farmland, against the wishes of the Semá:th (Sumas) First Nation, whose food and culture depended on it. In November 2021, an atmospheric river flooded that former lakebed, Sumas Prairie, forcing evacuations and killing hundreds of thousands of farm animals. Good planning works with physical processes instead of against them.