Summer mortality down compared with 2015–2019, but the risk remains high

Last Thursday, the Ministry of Health convened the Daily Mortality Surveillance System (Sismg), coordinated by the head of the Department of Epidemiology at ASL 1 in the Lazio Region, Paola Michelozzi, to request immediate feedback on the impact of the ongoing heatwave. The system enables the prompt detection deaths in Italy’s major cities; the first estimates of ‘excess mortality’ linked to the extreme heat of recent days are expected by next week.

Projections estimate hundreds of deaths attributable to rising temperatures. This is corroborated by several recent studies published in *Nature Medicine*, *ISGlobal* and *Lancet Countdown*, to name but a few. The Grantham Institute report from Imperial College has estimated the number of deaths attributable to climate change in 12 major cities (including the Italian cities of Rome, Milan and Sassari) affected by the heatwave of June 2025 (23 June–6 July): of the 2,305 deaths attributable to the heat, 64% (1,504) are thought to have been caused by ongoing climate change resulting from human activities. According to the study, Milan is one of the cities with the highest estimated number of deaths (499, of which 317 are attributable to climate change), followed by Paris and Barcelona.

However, these are estimates, derived from epidemiological models that enable us to estimate excess mortality attributable to heat, but they are not based on observed cases. This is the focus of the integrated system coordinated by Dr Michelozzi: ‘Our most recent findings have instead highlighted a reduction in the impact of extreme temperatures on mortality in Italia: analysis of data from 2024 and 2025, compared with that of the two preceding years (2022 and 2023) and against a reference period (2015–2019), has shown a much lower heat-related risk’.”

Despite a 22% increase in summer mortality in 2022, deaths over the last two years have actually been lower than expected (-4% during the summer of 2025 in the 54 Italian cities monitored). “This could be due to the preventive and climate adaptation measures implemented by local authorities,” explains Michelozzi. Italy is, in fact, one of the few European countries to have a plan to prevent the health effects of heatwaves.

Be careful, though, because this trend could also be linked to a distinctly Italian ‘phenomenon’ and may not necessarily last long: ‘The impact of Covid-19 has in fact led to a decline in the elderly and most vulnerable population, who are particularly susceptible to extreme heat. For this reason, it will be important to see whether this trend continues over time, including this year.”