Global Heat Stress Puts 70% of People at Risk

A study published in *Nature Climate Change* finds that exposure to extreme heat (heat index ≥ 46 °C) has risen sharply over the past five decades, adding more than a billion people to the risk zone. Today about 70 % of the world’s population faces at least 90 days per year with a heat index of 38 °C or higher, and 21.9 % experience conditions classified as extreme heat.

The increase spans all continents; Europe, South America, North Africa and the Arabian Peninsula show the largest rises. Heat stress now combines daytime temperature, humidity, solar radiation and wind, limiting the body’s ability to cool down even at night.

Health experts warn that children are especially vulnerable. In extreme heat, infants and preschoolers can quickly become dehydrated, develop heat‑stroke, electrolyte imbalance and multi‑organ failure. The study estimates roughly 559 million children are already exposed to dangerous heat levels, and the condition can worsen cardiovascular, respiratory and mental‑health problems.

Authorities recommend keeping children hydrated, avoiding exposure between 10 a.m. and 4 p.m., providing shade, lightweight clothing and well‑ventilated spaces to reduce risk.