Observed Trends in Health and Agricultural Temperature Indices across Canada: 1949–2024

Trends in health and agricultural indices based on the fourth generation of Canada's homogenized daily temperature dataset are examined for 1949-2024. Health indices are characterized by warm and cold spells, heatwaves and cold waves, indices associated to thermal comfort, and to heating and cooling requirements. Agriculture temperature-based indices include those related to damaging cold and heat, and to growing season. The results show that the frequency and duration of warm spells have increased across Canada, mainly in the northern and western regions, while a small decrease is observed in the frequency and duration of cold spells across the country. Heatwaves are more frequent in Canada, especially in the north, British Columbia and Atlantic provinces whereas the frequency of cold waves has decreased across the country, mostly in the north and west. The number of summer days and hot days above 30°C have increased in the southern regions, although that some decreasing trends are found in the number of hot days in the Prairies. The number of tropical nights (when night temperature remains above 20°C) has increased in southern Ontario and Quebec. Heating degree-days have decreased across the country whereas cooling degree-days have increased at most stations in the south. All agriculture cold-related indices, including ice days and frost days, have decreased. The annual highest daily maximum and lowest daily minimum temperatures have increased during the past 76 years, although that some decreasing trends are found in the highest daily maximum temperature in the Prairies. Overall, the growing season is now longer with an earlier start and later end to the season, and the number of growing degree-days has increased across the country.