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Municipal Heat Response Planning

Health risks from extreme heat exist and continue to grow in Simcoe Muskoka, impacting individuals and communities. Climate change is causing rising annual average temperatures and increasing the frequency and severity of extreme heat events.

The negative effects of extreme heat are preventable. Keeping people who live, work, and play in Simcoe Muskoka safe from extreme heat requires collaboration across multiple sectors, with roles from public health, local government, emergency management departments, community partners, and individuals. 

This page provides practical information and resources to assist municipal partners with developing and implementing strategies (i.e., a Heat Alert and Response System) to reduce the risk of illness and fatalities during heat events.

Heat Impacts and Risks of Extreme Heat

Extreme heat has direct and indirect negative effects on the health and well-being of people and communities. Everyone can be affected by heat. However, the risks are not equal for everyone due to differences in levels of exposure, sensitivity, and access to resources. People can be more susceptible to heat-related health risks early in the heat season because they are not yet acclimatized to higher temperatures. 

During an extreme heat event, the health risks and vulnerabilities can be amplified and compounded by other public health threats (e.g., COVID-19 pandemic, wildfires, extreme weather) and events (e.g., power outages) that occur at the same time or have recently happened. 

Understanding how heat impacts communities and people's health, and who is at greater risk and why, can help inform which protective measures will be put in place.

Heat and heat stress increases illness, fatality, and other adverse health outcomes in multiple ways, including heat exhaustion and heat stroke. The risk of acute illness (e.g., heart attack or stroke) among people with existing health conditions and impacts mental health (e.g., mood, mental illness, increased aggression, violence, and suicide) are also increased.

Extreme heat has social and economic costs to society. For example, the effects of extreme heat on outdoor workers can lead to work accidents, reduced work capacity, and loss of productivity. For some workers, this can also impact their income and overall well-being.

Extreme heat can increase economic costs as well as overwhelm a variety of systems communities rely on, such as:

  • Health systems: e.g., increased emergency room visits and hospital admissions.
  • Emergency systems: e.g., delayed 911 responses due to need that exceeds capacity.
  • Law enforcement: e.g., increased number of distress calls.
  • Infrastructure: e.g., increased infrastructure demands, including power usage that may result in power outages.
  • Community: e.g., increased use of green space, beaches, community pools, and splash pads.
  • Economic systems: e.g., reduced work productivity.
  • Educational approach: e.g., diminished learning capacity among students.

These systems are interconnected and when any of them are challenged, there are impacts on human health. For instance, power outages can put more people at risk to extreme heat because it impacts strategies used to stay cool (e.g., air conditioning). Losing power can also lead to reduced food safety, which may further stress health and emergency systems and create additional financial costs (i.e., replacing food) for individual households/organizations.

Along with extreme heat, average warming associated with climate change has additional health impacts that are outlined in Canada's Health in a Changing Climate report.

Some groups of people are at greater risk to the negative health risks of heat. It is important to understand who is at most risk to be able to develop and implement strategies that are equitable for all people.

The following groups of people are often considered to be at greater risk to the impacts of extreme heat:

  • Older adults
  • Infants and young children
  • People who are pregnant
  • People with pre-existing health conditions (e.g., heart disease, respiratory disease, diabetes)
  • People with reduced mobility
  • People who experience mental illness (e.g., schizophrenia, depression, anxiety)
  • People taking certain medications
  • People with substance misuse problems (e.g., drug users, people with alcoholism)
  • People who exercise in the heat
  • People who experience occupational exposure to heat (including hot outdoor and indoor environments)
  • People who live alone or are socially isolated
  • People with low socioeconomic status
  • People experiencing homelessness or marginal housing
  • Newcomers to Canada / people who do not speak English or French
  • Populations exposed to an urban heat island

Heat Islands

Due to the way urban environments are designed and built, they can have higher temperatures than surrounding and rural areas. This is referred to as the heat island effect, in which exposure to heat is magnified in urban areas. The graphic below illustrates the heat island effect across different environments.

Heat Islands

Image Source: Figure 1 from Durham Region. 2018. Adapted from EPA. 2014

Heat Alert Response Systems

Municipalities can take preventative action to reduce the risk of extreme heat as well as develop and implement Heat Alert and Response Systems (HARS) to reduce the risk of illness and fatalities during heat events. A HARS puts in place processes to alert the public of heat events and provide information, resources, and supports to help individuals take protective actions before and during an extreme heat event, especially for those who are at greater risk of negative health effects due to heat.

A HARS includes five elements and related tasks, as depicted in the graphic below, that are shared by stakeholders, including local governments, public health, and community partners.


Heat Alert Response Systems 
©2020 by Interior Health Authority. Adapted from Health Canada (2012). Used with permission.

NEW: Recommendations to municipalities in response to heat warnings (August 2022)

Strategies to Reduce Heat Exposure and Negative Health Outcomes

HARS is an important approach to reduce heat-related health risks during extreme heat events and is most effective when it is done together with preventative actions that provide long-term, sustainable protection from and resilience to heat and extreme heat. Preventative strategies provide protection from heat and extreme heat. They also provide a broad range of other health and economic benefits that support health and well-being of individuals and communities, providing a win-win situation.

Many of these measures overlap and provide additional health and economic benefits.

  • Develop and implement climate change mitigation and adaptation strategies to reduce heat-related hazards and build resilience.
  • Review and revise municipal emergency and extreme heat protocols that consider and apply information related to climate change, equity, and health.
  • Protect, conserve, and expand natural environments, blue- and green spaces and parks. Improve connectivity of greenspaces.
  • Adapt built environment infrastructure to reduce heat exposure and the urban heat island effect (e.g., increase blue- and green space/tree canopy, build shade structures, improve building codes, use reflective (high-albedo) materials, prioritize nature-based solutions, provide incentives for green and cool roofs, build thermal, comfortable playgrounds).
  • Encourage healthy community design principles and policies that encourage complete, connected, green communities.
  • Increase access to drinking water with public drinking fountains.
  • Implement systems for people to self-register to receive updates on response measures and heat alerts by telephone, email, and text.
  • Invest in strategies and policies that empower individuals to take personal actions to prevent heat harms (e.g., support equitable access to air conditioning; provide information and resources) and strengthen conditions of daily life (the determinants of health).
  • Review and revise occupational health and safety policies and strategies with a climate, equity, and health lens to protect people from heat effects.

All strategies should be equitable and target populations at greater risk.

Ontario's Harmonized Heat Warning and Information System

A Heat Warning and Information System (HWIS) is a coordinated provincial system that provides the criteria for issuing heat warnings in Ontario and is used in Simcoe Muskoka. A community's heat response plan is generally activated when specific criteria are met and Environment and Climate Change Canada (ECCC) issues a Heat Warning.

In Southern Ontario (including Simcoe Muskoka regions), a Heat Warning and Extended Heat Warning is issued by Environment and Climate Change Canada (ECCC) when the following criteria are met:

Notification TypeCriteriaDuration
Heat WarningDaytime temperatures are expected to be 31ºC or warmer and nighttime minimum temperatures of 20ºC or warmer.
Humidex values of 40ºC or more are expected.
2 days
Extended Heat WarningDaytime temperatures are expected to be 31ºC or warning and nighttime minimum temperatures of 20ºC or warmer.
Humidex values of 40ºC or more are expected.
3 or more days


1. Advance Notification - Environment and Climate Change Canada (ECCC) communicates the potential for a Heat Warning to SMDHU and other decision-makers a few days prior to a heat event (whenever possible). This advance notice provides time for partners to mobilize and prepare their community heat response.

  • In keeping with the standards outlined in Ontario's Heat Warning Information System, SMDHU will notify Community Emergency Management Coordinators (CEMCs) of the advance notice and associated details.

2. Heat Warning - When Heat Warning criteria are expected to be met, ECCC issues a Heat Warning. SMDHU will be notified by ECCC approximately one hour before the public, when possible. 

  • SMDHU will initiate the health unit's heat response plan (internal response), including communication activities.
  • SMDHU will notify CEMCs and request activation of the regional emergency plan for vulnerable populations.

3. Extended Heat Warning - When a Heat Warning is expected to extend for three or more days, SMDHU's Medical Officer of Health will issue an Extended Heat Warning.

  • SMDHU will initiate the health unit's internal response.
  • SMDHU will notify CEMCs and request activation of the regional emergency plan for vulnerable populations.

Weather changes quickly and ECCC may issue a Heat Warning with little or no advance notification.

SMDHU monitors ECCC resources and alerts during regular business hours Monday-Friday. In the event a warning is issued by ECCC during non-business hours, over the weekend or holidays, SMDHU will activate our internal response and notify CEMCs as soon as reasonably possible the following business day.

It is important to recognize that heat can pose threats to health and well-being of individuals below the extreme heat thresholds, particularly for people most at risk for extreme heat. Consider implementing actions that assist people most at risk before extreme heat thresholds are met by further implementing preventative strategies to reduce exposure, sensitivity, and increase adaptive capacity is required.

Climate Change Connection

In Simcoe Muskoka, climate change is leading to average rising temperatures, more hot days, and an increase in the frequency and severity of extreme heat events, resulting in greater health risks. Rising temperatures also influence other climate-related health hazards as vector-borne illnesses, food and water quality and quantity, drought, and wildfires.

Climate mitigation and adaptation strategies can effectively reduce the risk of extreme heat and climate-related hazards in the short and long-term. Climate action also protects and promotes health and well-being and provides economic savings for individuals, organizations, and governments.

Municipalities play a significant role in implementing climate action locally, and inspiring climate action by other levels of government, community partners, and the public.

Without greater adaptation efforts, projected increases in the frequency and severity of extreme heat and climate-events (e.g., extreme weather, drought, wildfires) will directly and indirectly affect health by causing more illness, injuries, and deaths. Immediate, rapid, and sustained climate mitigation is required to limit warming to 1.5ºC and associate risks to communities. Mitigation and adaptation work together to reduce risks of climate change. Often adaptation efforts have mitigation benefits and vice versa. Further, each approach helps reduce the cost of the other.



National and Cross-Provincial:


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