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Extreme Heat

What is the Durham Region: Heat Warning and Information System (HWIS)

Extreme heat (e.g. high temperatures and humidity levels) poses a significant health risk to Durham Region residents. Epidemiological evidence from recent extreme heat events in Canada and internationally has demonstrated a link between heat and excess morbidity and mortality. Heat-related illnesses are largely preventable, given appropriate notification and interventions.

Environment and Climate Change Canada is providing heat warning information to Ontario Public Health units. Durham Region Health Department (DRHD) in collaboration with other health units are continuing to work together for a harmonized Heat Warning and Information System for Ontario.

The key elements of this initiative are:

  • Communicate heat warnings to local municipalities, community partners and the public
  • Raise awareness about heat-related illness
  • Promote protective actions to take before and during a heat event
  • Identify, engage and support community partners who work with vulnerable populations that are at increased risk from heat and heat related illnesses
  • Work with local municipalities to improve and support their heat response plans

What are the heat alert levels?

The Durham Region HWIS has two heat alert levels. Environment and Climate Change Canada's meteorological services will provide support and notification to DRHD when weather surveillance indicates a forecasted heat event in our area.

Alert Level Forecast Condition Duration DRHD Communication
Heat Warning

Daytime highs greater then or equal to 31°C AND
nighttime lows greater then or equal to 20°C
Humidex of 40 or greater

2 days Public alert level. Issued by Environment and Climate Canada and communicated by DRHD through media and
Extended Heat Warning

Daytime highs greater then or equal to 31°C
nighttime lows greater then or equal to 20°C
Humidex of 40 or greater
At the discretion of Durham Region Health Department during extenuating circumstances (i.e. large scale power outage during a heat event)

3+ days Public alert level. Issued and communicated by DRHD through media and

Heat Warning Indicator Gauge

The following images will be posted on to advise the public what the current heat warning status is. A brief message below the warning will describe what the forecast or current conditions are. For current and forecast weather conditions for your area go to Environment and Climate Canada's website.

Early notification available only for community partners and local municipalities?

Enviornment and Climate Change Canada and Public Health Ontario has identified that a heat event may be detrimental to the heat vulnerable population. Community partners that work with the heat vulnerable groups are at an ideal position to employ strategies that may help mitigate and control the risks of heat exposure. DRHD will provide this information to interested community partners subscribed to receive our heat warning messages by email. This information will allow local municipalities and community partners to better prepare for the upcoming heat event and allow time to review their heat response plans.

Do you or your organization provide services for people who may be vulnerable to heat? Learn how to receive email notices regarding forecasted heat events.