600 Million People Can’t Stay Cool. The ‘Hot City’ Problem Is Growing

InnovationScience600 Million People Can’t Stay Cool. The ‘Hot City’ Problem Is GrowingByLaurie Winkless,Contributor.Forbes contributors publish independent expert analyses and insights. New Zealand-based physicist & science journalist fascinated by citiesFollow AuthorMay 29, 2026, 02:26am EDT--:-- / --:--This voice experience is generated by AI. Learn more.This voice experience is generated by AI. Learn more.LONDON, ENGLAND - MAY 26: A woman fans herself as another shelters from the sun as they wait to take a selfie next to a phone box in Parliament Square on May 26, 2026 in London, England. The UK has recoded the hottest May temperature on record with a blistering 34.8°C registered at Kew Gardens. Overnight temperatures also reached a record-breaking 21.3°C, marking the country's first-ever spring "tropical night." This extreme heatwave has triggered Amber Heat-Health Alerts across central and southern England. (Photo by Carl Court/Getty Images)Getty ImagesNew research confirms that extreme heat is reshaping city life, and we’re not prepared for what that means for the futureHeatstroke has killed at least 16 people in southern India so far this year. The UK reported its hottest-ever day for May, at 35.1°C in southwest London. Japanese workplaces report a total of 1,803 people experiencing heatstroke in 2025 (up from 546 in 2024). And professional tennis players are collapsing on the Roland Garros court. It seems that everywhere you look at the moment, you’ll find news of people struggling with heat…and that’s all before the arrival of the “super El Niño” that’s predicted to intensify weather events around the globe in the coming months.There’s something similar happening in the scientific literature, too. I’ve found a group of research papers, all published in the past few weeks and written by scientists from a range of disciplines, that together paint a coherent – and worrying – picture of extreme heat in the cities we call home. Let’s start wit...