Lorraine Williamson
An estimated 5,428 deaths in Spain were attributable to high temperatures during the astronomical summer, according to the country’s mortality-monitoring system. The new figures come at the end of a record-breaking season in which Spain endured its hottest summer for at least 150 years and an unprecedented number of days under heatwave conditions.
Spain’s extraordinary summer heat is estimated to have contributed to more than 5,400 deaths between the summer solstice on 21 June and the arrival of astronomical autumn on 23 September.
Figures from the MoMo mortality-monitoring system, operated by the Instituto de Salud Carlos III, put the current estimate at 5,428 deaths attributable to high temperatures during that period. The figure adds another stark measure of the human impact of a summer characterised by prolonged and unusually intense heat.
What does ‘attributable to heat’ actually mean?
The figure does not mean that 5,428 people had heat recorded as their individual cause of death. MoMo uses statistical modelling to estimate mortality attributable to temperature by analysing observed and expected deaths alongside the effect of unusually high or low temperatures.
The system is designed to identify patterns of excess mortality associated with extreme temperatures and other periods of unusually high mortality. Its most recent figures are also provisional because reported deaths can arrive late, meaning estimates are continually recalculated and may change over the coming weeks.
Spain endured its hottest summer on record
The mortality figures follow an exceptional season for temperatures across Spain. AEMET’s final climate assessment found that summer 2026 was the hottest in Spain since at least 1869, with temperatures well above normal across the entire country.
June was extremely hot and the second warmest on record, while July became the hottest July in the historical series. August was the sixth warmest, while summer-like temperatures extended beyond the conventional season into the second half of May and the beginning of September.
The persistence of the heat was particularly remarkable. AEMET recorded 61 days under heatwave conditions across mainland Spain and the Balearic Islands during 2026, comfortably exceeding the previous record of 41 days in 2022.
Two of the summer’s heatwaves were exceptionally long. The July episode lasted 23 days, and the following heatwave continued for 24 days into August, making them respectively the third and second longest recorded in Spain since at least 1975.
Older people particularly vulnerable
The effects of prolonged heat are not evenly distributed across the population. Older people are particularly vulnerable, along with those living with chronic illnesses, people who live alone, and those exposed to high temperatures through their work.
Regional data released on Wednesday illustrate that impact. The Comunitat Valenciana recorded 586 deaths attributable to high temperatures during the astronomical summer, its highest figure since the current MoMo series began in 2015. Of those, 279 were recorded in Alicante province, 179 in Valencia and 128 in Castellón.
The region experienced three heatwaves during its hottest summer since records began in 1950, as well as a record 65 torrid nights, when minimum temperatures remained exceptionally high.
Summer temperatures are still lingering
Astronomical autumn officially began in Spain at 2.05 am on Wednesday, but temperatures are telling a different story. An analysis by RTVE using an AEMET-based methodology calculates that summer-like conditions have already persisted for 119 days in 2026, five days longer than the previous record set in 2023.
The analysis suggests the thermal summer is not yet over. Forecast temperatures could extend the run further, underlining how increasingly blurred the traditional boundaries between Spain’s seasons have become.
With autumn now officially under way, the final mortality figures will take several weeks to settle as MoMo incorporates delayed data. What is already clear is that 2026 has combined record-breaking temperatures, prolonged heatwaves, and thousands of estimated heat-attributable deaths, making it one of Spain’s most consequential summers on record.