A heat wave gripping southern Ontario this week, with temperatures approaching 42°C with humidity and orange-level heat warnings in effect across much of the region, is a reminder of a risk category insurers have historically treated as background noise but are increasingly having to underwrite for directly.
Unlike floods, wildfires or windstorms, heat waves rarely trigger the kind of headline property damage that drives catastrophe designations, but insurers are increasingly recognizing their financial footprint across multiple lines.
According to Swiss Re, extreme heat can raise medical, life and workers' compensation claims, particularly for outdoor and vulnerable populations, while also increasing liability exposure for employers and institutions that fail to adequately protect people from heat-related harm.
Crop and livestock losses tied to extended heat can also flow into agriculture insurance claims, and heat-related strain on infrastructure and machinery can trigger business interruption and engineering claims where buildings or equipment aren't designed to tolerate higher temperatures.
New federal workplace rules add a compliance dimension to this summer's heat. Amendments to the Canada Occupational Health and Safety Regulations that took effect in February 2026 introduced detailed thermal stress requirements for federally regulated workplaces, including the use of established heat threshold values, humidex monitoring, and specific training and reporting obligations.
The changes reflect a broader shift toward treating heat as a routine operational risk rather than an occasional emergency, which has direct implications for employers' liability coverage.
That liability exposure isn't hypothetical. At Insurance Bureau of Canada's 2026 InSight Summit, real estate risk professionals pointed to last summer's Toronto heat wave as a case study, noting reports of tenants pursuing legal action against landlords over HVAC systems that failed to keep units adequately cool.
Panelists described that as both a legal and reputational risk that real estate owners and operators need to actively plan for, rather than treat as a secondary concern behind more traditional perils like flood or wildfire.
Heat waves are also part of a broader shift in Canada's climate risk profile that insurers have flagged as increasingly material.
Reinsurance industry data presented at IBC's 2026 InSight Summit showed that climate-related secondary perils, the category that includes heat, drought, severe convective storms and wildfire, now account for 50% to 55% of Canada's total natural catastrophe loss pool, up from around 30% in the first decade of the 2000s, even as earthquake remains the country's single largest peak risk.
That shift has pushed insurers toward probabilistic modelling rather than historical loss data alone when pricing property and casualty risk in heat-exposed regions.
None of this means this week's heat wave will generate the kind of headline insured losses associated with a major flood or windstorm event.
But the pattern across workers' compensation, liability, agriculture and property lines suggests insurers, brokers and risk managers have reason to treat sustained extreme heat as a recurring underwriting consideration rather than an occasional anomaly, particularly as Environment Canada's warning preparedness meteorologists note that while this week's heat isn't expected to break historical records, it continues a pattern of more frequent and prolonged heat events across the province.
