How Winnipeg chose its Heat Alert and Response System alert triggers

The Winnipeg HARS Advisory Committee, which is responsible for guiding the development of the HARS, established a Heat Scientific Group led by the provincial Medical Officer of Health (Environmental Health). The Group includes officials from provincial public health, the Winnipeg Regional Health Authority, Environment Canada, provincial communications office and provincial health emergency management. Its mandate includes evaluating existing evidence demonstrating that heat is a health risk in Manitoba (rural and urban), identifying HARS best practices and deciding on alert triggers. To develop appropriate triggers, multiple factors were considered, including humidity and temperature, the location of vulnerable populations, accuracy of weather forecasts, and existing capacity for surveillance of heat illnesses. Historical data and their correlation with mortality were also examined.

Winnipeg, Manitoba, developed a multi-level alert protocol with multiple triggers as part of its HARS. The alert levels include:

• Heat Pre-Alert—communication only to internal partners
• Heat Alert 1—communication to the public and community stakeholders, as well as initiation of some response measures if required
• Heat Alert 2—activation of some response measures and enhanced messaging
• Heat Alert 3—delivery of aggressive response measures, more targeted messaging and increased community mobilization