At least 35,000 more people died during Europe’s four record-breaking, back-to-back heatwaves this summer than would normally be expected, according to incomplete figures from barely half the continent.

Excess mortality in three of the EU’s larger countries – Germany, France and Spain – alone has already exceeded 25,000, according to the provisional national figures, and experts say the toll will rise significantly once August totals are consolidated.

The consecutive heatwaves across western Europe since May shattered all-time historical temperature records across hundreds of weather stations, and France recorded its hottest national average day on record.

Records fell for three straight days in Germany in late June, when 46 stations topped 40C (104F), while Spain endured persistent highs above 42C. Scientists say human-made global heating is making such extreme events more frequent and intense.

The death toll is highest in Germany, which late last week reported an estimated 14,000 heat-related deaths from 6 April to 9 August. The Robert Koch Institute (RKI) public health agency said 9,600 people had died in the week of 22-28 June alone.

Systematically compiled EU-wide excess mortality figures, available since 2008, show the only other summer week in which a higher rate of additional deaths has been recorded was in July 2022, when Covid-19 was still active.

This summer has been by far the worst for heat-related deaths in Germany since records began. The previous high in the EU’s most populous country was 8,900 in 2018. Heat-related deaths during normal summers are often below 2,000, RKI said.

Figures from the Carlos III health institute’s mortality monitoring system suggest 4,947 deaths in Spain can be attributed to heat between May and this week, making 2026 Spain’s worst year on record for heat-related deaths, exceeding the 4,520 recorded in 2022.

Different countries calculate and present their data in different ways. Spain and Germany model estimated heat-related deaths in real time, comparing daily temperatures and mortality rates to calculate deaths attributable to heat.

Such estimations are necessary because heat is rarely stated as a direct cause of death. In most cases, heat aggravates a pre-existing health conditions such as respiratory or cardiovascular disease, and victims die of a heart attack, stroke or kidney failure.

Final attribution can take weeks or even months, and many countries have yet to release figures even for early August. Karl Lauterbach, a former German health minister, said last week that figures released so far would probably prove to be underestimates.

France, where more than 500 weather stations recorded temperatures higher than 40C and at one stage 98% of the country was under heat alerts, reports an initial “all causes” excess death figure and definitive attribution later.

Its national health agency said last week that “all cause” excess deaths between late May and 22 July stood at 7,300. August figures were not yet available and initial data was based on electronic death certificates, which account for only 80% of total mortality, it said.

Italy, whose national heat surveillance system uses local municipal data, meaning it is often subject to significant delays, has so far only reported incomplete real-time indicators rather than a consolidated national death toll.

Modelling suggests 2,700 more people died than usual between 22 and 28 June alone and epidemiologists have said the country’s total heat-attributable death toll would probably be between 5,000 and 8,000 by the time it is formally recorded.

Other European countries to have already reported excess death tolls include the UK, where the health security agency said in July that its modelling suggested the May and June heatwaves had resulted in 2,877 heat-associated fatalities in England.

Belgium has said its preliminary data shows it recorded a 39% increase in mortality between 18 and 29 June, equating to 1,222 additional deaths, and the Netherlands has said at least 900 more people than usual died between 22 June and 5 July.

A rapid modelling study cited by the European Commission estimates that 1,070 more people than usual died in Poland during the late-June heatwave, and Swiss public health authority data suggests excess heat-related deaths of 220 in the same week.

Early figures from Luxembourg, Greece, Romania, Bulgaria and Denmark indicate about 40 excess deaths in each of those countries. Agence France-Presse has calculated that areas inhabited by more than 80 million Europeans experienced temperatures above 40C this summer.

The World Health Organization said in May that heat-related mortality in its European region had increased by more than 30% over the past 20 years and was on course to climb significantly as a result of the climate crisis and population ageing.