Overview

• An IIED analysis of 43 politically significant cities shows average annual days above 35°C rose from 1,062 in 1994–2003 to 1,335 in 2015–2024.
• Across the cities, 2024 recorded 1,612 very hot days, the highest in the dataset, with recent peak years also including 2023 and 2019.
• Increases were widespread, with days over 35°C doubling in Rome and Beijing and tripling in Manila, while Madrid’s average rose from 25 to 47 days.
• Researchers say elderly people, low-income residents and those in informal settlements face the greatest risk, as human-driven warming intensifies heatwaves.
• The Global Center on Adaptation launched The Heat is On campaign to expand cooling centers, shaded rest areas, early-warning systems and climate-smart work schedules.