Real-time forecast of heat-related excess mortality during June 2025 heatwave

Authors:
Dr Garyfallos Konstantinoudis, Grantham Institute for Climate Change and the Environment, Imperial College London

Assistant Professor Malcolm Mistry, Environment & Health Modelling Lab, London School of Hygiene and Tropical Medicine

Professor Antonio Gasparrini, Environment & Health Modelling Lab, London School of Hygiene and Tropical Medicine

* the authors contributed equally to the report.

It is well established that extreme heat increases the risk of mortality. During the exceptionally hot summer of 2022, an estimated 61,672 heat-related deaths occurred across 35 European countries,1 including approximately 3,000 excess deaths due to heatwaves in England.2 As the climate continues to warm, periods of extreme heat are becoming more frequent and intense.

In this report, we estimate the expected excess deaths from exposure to heat during the first heatwave of 2025 in England and Wales, specifically between 19-22 June at small geographic scales.

Key points

• About 570 people in England and Wales are expected to die as a result of high temperatures from Thursday to Sunday (19-22 June).
• It is the first real-time analysis in 2025 on excess heat deaths by researchers at the London School of Hygiene & Tropical Medicine and Imperial College London.
• The study uses decades of UK data to understand risk relationships in 34,753 areas across England and Wales to predict the excess mortality during this heatwave. The researchers estimate a peak of 266 excess deaths on Saturday when the heat will be most intense and expect London to have the greatest number of excess deaths with 129.
• This assessment highlights how extreme heat poses a growing threat to public health in the UK and follows a study published on Friday that found the heatwave about 10 times more likely and 2-4°C hotter due to climate change.