The five-year moving average of the Climate Actuarial Index (CAI), which tracks changes in extreme weather events and sea level rise, saw a modest increase in winter 2025 compared to fall 2024.
The index now stands at 1.37, based on a reference period average of zero spanning from 1961 to 1990.
In the previous update released in May 2025, covering fall 2024, the CAI was at 1.35. The rise is “primarily due to changes in consecutive dry days and wind power,” according to the statement issued on August 21.
Compared to Winter 2020
The five-year moving average was updated following the inclusion of seasonal data for winter 2025. For Canada and the United States, the winter 2025 figure came in at 1.38.
Because the CAI’s five-year moving average is recalculated quarterly, the new winter 2025 data replaces the winter 2020 figure, which stood at 1.18.
When CAI values rise above the baseline average of zero, it indicates that extreme weather events are becoming more frequent and that sea level rise is ongoing.
