World’s major cities hit by 25% leap in extremely hot days since the 1990s

People cross a street on a hot day in Tokyo. Japan hit its all-time record temperature of 41.2C in July, with more than 10,000 people taken to hospital. Photograph: Kazuhiro Nogi/AFP/Getty Images

The world’s biggest capital cities are now sweltering under 25% more extremely hot days each year than in the 1990s, an analysis has found. Without urgent action to protect millions of people from high temperatures, more and more will suffer in the dangerous conditions, analysts said.

From Washington DC and Madrid to Tokyo and Beijing, the analysis shows a marked rise in hot days as the climate crisis intensifies. Overall, the assessment by the International Institute for Environment and Development (IIED), found the number of days above 35C in 43 of the world’s most populous capital cities rose from an average of 1,062 a year from 1994-2003 to 1,335 from 2015-2024.