Extreme heat poses growing risks to the health of Canadians. Public health and emergency management officials in several Canadian communities are developing interventions to reduce heat-health risks and to prepare for the expected increase in the frequency, duration and severity of extreme heat events due to climate change. To help Canadians protect themselves and their families, health authorities are seeking information about the most effective public health interventions to assist those at risk. A range of actions to safeguard health are being taken, but many remain untested. In support of these efforts, Health Canada is taking action to help Canadians and their communities become more resilient in the face of a changing climate. As more communities in Canada begin to develop systems to reduce risks to health from extreme heat, they will require effective strategies to protect health.A key adaptation step to protect people from extreme heat events is the development and implementation of Heat Alert and Response System(s) (HARS) by public health and emergency management officials. Heat Alert and Response Systems to Protect Health: Best Practices Guidebook provides an overview of health risks from extreme heat and offers evidence-based strategies for alerting health authorities and the public when hazardous conditions arise. It is intended for use by policymakers, planners and service providers involved in protecting citizens from extreme heat events. The Guidebook is designed to help develop interventions tailored to the needs of a specific community.