As Canada experiences more frequent and intense heat waves due to climate change, new research is sounding the alarm: extreme heat is putting children’s health at serious risk.
A new study published in Environmental Health (2025) by Centre Member Eric Lavigne, analyzed over 6 million pediatric emergency department (ED) visits and hospital admissions among children in Ontario from 2005 to 2015. The findings were striking:
On days of extreme heat—defined as two consecutive days above the 99th percentile of local temperatures—hospital admissions and emergency department visits surged for a range of conditions:
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Respiratory illnesses increased by 26%
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Asthma admissions rose by 29%
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Infectious diseases jumped by 36%
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Emergency department visits for heat-related illnesses more than tripled.
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The risk was especially high for younger children under 5y of age and teens aged 13–18, with girls more likely to be hospitalized than boys.
Why are kids so vulnerable? Children’s bodies don’t regulate temperature as efficiently as adults. They sweat less, have a higher surface area relative to their body size, and depend on adults to manage their exposure. They also spend more time outdoors - especially in summer, notes Lavigne.
Yet, most public health heat alerts are based on data from adults, not children. In fact, when Lavigne and his colleagues tested lower temperature thresholds, they found that the health impacts for children largely disappeared. This means that current systems may not be stringent enough to protect children from serious health impacts.
What can be done?
This study points to a clear need for child-specific climate health strategies, including
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Lowering heat alert thresholds for children and issuing targeted warnings
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Tailoring public health messaging to caregivers, schools, and childcare providers
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Designing urban environments with shaded play areas, cooling centers, and green infrastructure
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Expanding research into long-term and mental health impacts of heat on children
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Integrating pediatric data into emergency planning and climate adaptation policies
As Canada’s summers grow hotter, protecting children's health needs to be a key part of how we adapt to our changing climate.
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