Climate change and heatwaves: Improving Ontario’s harmonized heat warning and information system

Created in 2015, Ontario’s Harmonized Heat Warning and Information System (HWIS) has never been evaluated for its processes and implementation. This paper evaluated the HWIS’s processes using a guidance report published by the World Meteorological Organization and World Health Organization. It also evaluated public health units’ implementation of the HWIS using information found on their websites. The results showed the HWIS lacks monthly threshold values, evaluation processes, and a wider action plan. In the implementation of the HWIS, public health units have failed to post on their websites all 15 heat health messages and locations and hours of local interventions. Six recommendations are made to Public Health Ontario, public health units, and Ontario Ministry of Health to improve on the processes and implementation of the HWIS. As climate change increases the frequency and intensity of heatwaves, an improved HWIS can reduce the incidence of heat-related illness and deaths in Ontario.