Here are key facts and figures published by the World Health Organization (WHO) on hot weather, high temperatures, heat extremes, and public health due to our climate change crisis:
Heat constitutes a significant risk to environmental and occupational health, standing as the primary weather-related cause of death. It can worsen pre-existing conditions such as cardiovascular disease, diabetes, mental health issues, and asthma and elevate the likelihood of accidents and some infectious diseases. Heatstroke poses a serious medical threat with high mortality rates.
The growing impact of climate change on extreme heat exposure is worldwide. Heat-related mortality has increased significantly, especially among individuals over 65, increasing by approximately 85% from 2000–2004 to 2017–2021. Studies from 2000–2019 indicate an average of 489,000 deaths annually due to heat, with Asia and Europe accounting for 45% and 36% of these deaths, respectively.
Susceptibility to heat is influenced by physiological factors such as age and health and exposure elements like occupation and socio-economic status. The WHO provides guidelines for managing extreme heat risks. An integrated approach to climate action, preparedness, and risk management can significantly reduce heat-related health impacts now and in the future.
References
- Lancet Countdown: Heat-related Mortality. 2023. https://lancetcountdown.org/explore-our-data
- Zhao et al., 2021 Global, regional, and national burden of mortality associated with non-optimal ambient temperatures from 2000 to 2019: a three-stage modeling study https://pubmed.ncbi.nlm.nih.gov/34245712/
- Heat-related mortality in Europe during the summer of 2022 https://www.nature.com/articles/s41591-023-02419-z
- Hot weather and heat extremes: health risks. The Lancet. https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(21)01208-3/fulltext
© 2025 WHO.
(Source: www.who.int/news-room/fact-sheets/detail/climate-change-heat-and-health)
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