Rapid Extreme Weather Event Attribution system
Backgrounder
Canada's Rapid Extreme Weather Event Attribution system
The Rapid Extreme Weather Event Attribution system analyzes extreme weather events quickly and shows how human-caused climate change can impact the likelihood of extreme weather events happening. An extreme weather event is when we get unusual or unseasonal extremes compared to historical data.
The system is new for Canada and is still developing. This season, Environment and Climate Change Canada expanded the Rapid Extreme Weather Event Attribution system to better understand the role of climate change in extreme precipitation. It takes about 24 hours after a severe precipitation event stops to get results. Scientists use climate models to compare two different climates: the climate of the 1800s and the climate of today.
Understanding precipitation
Precipitation is any form of water that falls from the sky—rain, freezing rain, sleet, hail, and snow. The system analyzes the most extreme precipitation events, which are most commonly heavy rainfall. Researchers use climate models to determine how much more likely each event was made by human-caused climate change.
On average, precipitation rates in Canada are increasing, but the amount of precipitation varies widely across the country. Some locations on the West Coast receive an average of 3,000 millimetres of precipitation or more in a year. Annual precipitation can be as low as 300 millimetres in parts of the Prairies or about 200 millimetres in the Far North (CCCR2019, Changes in Temperature and Precipitation Across Canada).
Extreme precipitation analysis
Since June 2025, researchers have analysed 42 of the most extreme precipitation events across Canada and determined that 39 were made more likely to occur by human-caused climate change.
Three additional events were found to have been made much more likely to occur. This means that these events were at least 2 to 10 times more likely in today’s climate than a pre‑industrial one:
Atlantic Canada: Happy Valley-Goose Bay, Labrador (eastern)
- Date: July 18, 2025
- Total accumulated precipitation: 36.0 millimetres
- Portion of July’s total precipitation average: 32.8%
Southern Qikiqtaaluk: Western Baffin Island, Nunavut
- Dates: July 11, 2025
- Total accumulated precipitation: 20.4 millimetres
- Portion of July’s total precipitation average: 40.6%
Atlantic Canada: Happy Valley-Goose Bay, Labrador (eastern)
- Date: November 1, 2025
- Total accumulated precipitation: 39.9 millimetres
- Portion of November’s total precipitation average: 43.0%
As extreme precipitation becomes more frequent, Canadians should monitor weather forecasts, take all alerts seriously, and get prepared by developing an emergency plan and being ready to adjust their travel plans. Canadians can download the WeatherCAN app to receive weather alert notifications directly on their mobile devices.