A prolonged and intense heatwave has caused thousands of excess deaths across Europe, with the United Kingdom, Italy and France among the worst-affected countries, while Japan and the United States also grapple with dangerously high temperatures. A joint study by Imperial College London, the London School of Hygiene & Tropical Medicine and the UK Met Office estimates that 2,736 heat-related deaths occurred in England and Wales during May and June, of which around 2,200 were recorded in the final week of June alone. Data from the EuroMOMO mortality monitoring network indicates more than 10,000 excess deaths across Europe in that same peak week, predominantly among people aged over 65. In Japan, local media report more than 4,500 hospitalisations for heatstroke in a single week, with temperatures reaching 38.4°C in Kochi prefecture.

In Italy, the health ministry placed 16 cities under a red alert, the highest risk level, as temperatures were forecast to hit 45°C in inland Sardinia and 40°C in Florence and Rome. One person died in a car crash during a violent downpour in Emilia-Romagna, and authorities in Lombardy issued an orange alert for thunderstorms, hail and wind gusts of up to 150 km/h. In the United States, a heat dome stretched from the West Coast to the East Coast, placing nearly 100 million people under heat alerts; New York City activated a “Code Red” emergency and opened cooling centres as temperatures reached 41°C. Swedish meteorologists warned of an extreme risk of forest fires across the southern half of the country, while Morocco’s weather service issued an orange alert for several provinces, with temperatures expected to reach 46°C.

Researchers from the World Weather Attribution group said the June heatwave in Europe would have been “virtually impossible” without human-caused climate change. The UK Met Office’s annual climate report noted that the number of days above 30°C in London had more than quadrupled compared with the 1961–1990 average. A municipal climate profile for Milan projected that by the end of the century the city could experience up to 120 tropical nights per year, with average temperatures more than 5°C higher than in the late 20th century. Medical experts in Italy and the UK linked the extreme heat to increased irritability, workplace accidents and violent crime, though they cautioned that isolating heat as a sole cause remains methodologically difficult.

While the immediate death toll is provisional and subject to revision, health authorities across Europe have urged vulnerable populations to stay indoors and hydrated. In several Italian regions, outdoor work was banned during the hottest hours, and delivery riders staged protests demanding better heat protections. The heatwave is expected to persist in southern Europe and the US through the weekend, with some relief forecast for northern Europe as cooler air moves in. The full scale of the health impact will not be known for weeks, officials said.