Why water security matters to cities under extreme heat in the Global North

The summer of 2025 brought Europe to a boiling point. Record-breaking heatwaves swept the continent starting in mid-June, with temperatures soaring above 46 °C in parts of Spain and Portugal 1 . In Barcelona, nights were torrid, with minimum temperatures above 25 °C for 10 days 2 , making restful sleep nearly impossible. Against this backdrop, cities such as Paris and Barcelona are bracing for a future where daily highs of 50 °C could be reached 3 , 4 . Conditions of extreme heat are already straining public health systems 5 , leading to spikes in hospitalizations 6 , especially in older adults 7 , and increased mortality 8 . It is estimated that the 10 days of extreme heat in late June and early July 2025 in Europe resulted in ~2300 excess deaths across 12 major European cities, with 65% of the deaths attributed to the effects of climate change 9 . Furthermore, heatwaves interact with the Urban Heat Island effect in ways that may exacerbate heat stress in cities compared to suburban and rural areas 10 .