Cumulative Lifetime Heatwave Exposure for Canadian Children in a Warming Climate

Heatwaves are among the deadliest climate extremes, with children especially vulnerable due to physiological sensitivity and limited adaptive capacity. Yet cumulative lifetime exposure of children remains poorly quantified, particularly in high-latitude countries such as Canada, where warming is occurring at roughly twice the global average. Here, we present the first national-scale assessment of Lifetime Heatwave Exposure (LHE) for Canadian children under multiple global warming pathways.

We integrate high-resolution temperature observations, downscaled CMIP6 climate projections, and demographic data to estimate the number of severe heatwave events children are expected to experience over their lifetime. Heatwaves are defined using locally relevant thresholds based on exceedance of the 98th percentile of daily maximum temperature, ensuring consistency across Canada’s climate zones. Exposure is evaluated across warming levels from 1 °C to >5 °C at sub-provincial population scales.

Our results demonstrate a clear generational shift in heat exposure. Under 3 °C warming, over 80% of Canadian children are projected to experience unprecedented lifetime heatwave exposure exceeding the historical maximum. Analysis of 45 major historical heat events shows that 70% of reported heat-related deaths occurred during LHE-level events, including the 2021 Pacific Northwest heat dome, when 447 excess deaths were recorded in Vancouver alone. Projections indicate a nationwide transition from rare, once-in-a-lifetime heatwaves to recurrent generational hazards, with western provinces reaching full exposure earliest and eastern and northern regions converging rapidly by mid-century.

By shifting focus from short-term extremes to cumulative lifetime exposure, this study introduces a child-centric, policy-relevant metric for climate risk assessment. The findings highlight growing intergenerational inequity and underscore the urgency of global mitigation alongside targeted local adaptation—such as urban greening, cooling infrastructure, and heat-health early-warning systems—to protect current and future generations of Canadian children.