What Canada’s colour-coded heat warnings mean as temperatures soar

Millions of Canadians are currently under heat warnings as a heat dome intensifies across the country. Environment Canada has issued yellow and orange alerts across Ontario, Quebec, Alberta, Saskatchewan, and the Northwest Territories, signaling a significant threat to public health and safety.

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tell you at a glance what risks the weather may pose to you.

The colour-coded system, introduced in late 2025, aims to provide a clear, at-a-glance understanding of weather risks. Yellow alerts indicate moderate, localized impacts that may cause disruption or health issues. However, the current situation has escalated to orange alerts, which are less common and signify severe weather likely to cause significant, widespread, and potentially prolonged health impacts and disruptions.

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more easily communicate the severity or the seriousness of particular weather events to agencies that need to know about it.

An extreme heat event is defined by daily temperatures reaching warning thresholds for at least two consecutive days without overnight relief. Environment Canada aims to issue these warnings 18 to 24 hours in advance. Orange alerts, in particular, suggest high temperatures lasting three or more days, prompting communities to open cooling centers. The severity of these warnings underscores the serious health risks associated with prolonged exposure to extreme heat, including increased illness and mortality.

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moderate, localized and/or short-term.