More than 34,600 people died in five Western European countries due to heat this summer as the region posted its hottest June, July and August on record, according to a Bloomberg compilation of mortality estimates from different agencies.

Spain saw its deadliest summer since records began in 2015, with 5,805 excess deaths attributable to heat between May 15 and Sept 30, according to data from the Instituto de Salud Carlos III that was made public on Thursday. In France, three heat waves led to an estimated 7,824 deaths, the highest toll since at least 2015, according to provisional figures from the national public health agency. Germany, the UK and Belgium also recorded elevated heat-related mortality.

“Spain has recorded 61 heat wave days over the summer, with four heat waves, a fifth in September and extreme heat episodes in May,” said Diana Gómez, head of the mortality monitoring system at ISCIII. “All of that has resulted in an increase of deaths attributable to heat.”

Heat can exacerbate existing illnesses and is particularly dangerous for vulnerable people including young children, the elderly and workers exposed to high temperatures over long periods of time. Western Europe faced extraordinary heat throughout the summer, with average temperatures for the region 2.5C above the average between 1991 and 2020, according to the latest monthly report by Earth observation program Copernicus.

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European data indicate temperatures over the summer were the highest since at least 1979 across virtually all of England, Wales and Belgium, as well as most of France, Spain, Italy, Switzerland and Austria. The previous record was set in 2003, when countries including the UK, France and Germany recorded tens of thousands of heat deaths and healthcare services struggled to cope with cases of heat stroke, forcing authorities to improve emergency responses and hot-weather services.

On 17 days this year, at least 60 percent of Western Europe experienced temperatures above 30C (86F), according to a Copernicus report released on Friday. That compares with 11 days under the same conditions during the summer of 2003. A record 52 percent of the European continent experienced temperatures of 38C or higher during the summer, which qualifies as “very strong” heat stress under the Copernicus ratings system.

In Spain, this summer’s heat deaths exceeded the previous record of 2022 by more than 1,000, the ISCIII found. The worst day was July 10, according to the public health research institute, which calculates excess mortality by comparing the daily total of deaths to average mortality rate in previous years and factoring in temperature thresholds for each of the country’s 50 provinces.

“Thresholds have been surpassed in every province for many days,” Gómez said. “Ours is the only system that issues daily estimates and, since we have a lot of experience in this field, several European countries have been in touch with us over the past few days.”

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In Germany, deaths reached the highest level in at least a decade, with about 16,000 heat-related deaths between April 6 and Sept 13, according to the Robert Koch Institute, the federal government agency responsible for disease control. About 9,600 people died as a result of the heat wave at the end of June, which was the worst on record for Western Europe. The country’s previous record was about 9,000 heat deaths in 2018.

Preliminary data from Santé Publique France indicate heat deaths in France this summer hit the highest number since at least 2015 due to three major heat waves in June, July and August. The government agency is expected to publish a definitive mortality report early next year.

That compares with 5,700 estimated deaths last year. In 2003, researchers at the University Paris 5 found that devastating temperatures that year led to 14,800 excess deaths in August alone.

In the UK, heat waves caused an estimated 2,877 deaths in May and June this year, according to the UK Health Security Agency, which is due to release a final mortality report covering the whole season next year. In Belgium, 2,112 people died between June 18 and July 12, according to Sciensano, the country’s public health institute.