Heatwaves caused an estimated 2,700 deaths so far this year, study finds

More than 2,700 people are estimated to have died as a result of record breaking temperatures during the May and June heatwaves, a study has suggested.

Of those deaths, it is thought just over 40 per cent died as a direct result of climate change, researchers at Imperial Collegee London, the Met Office and the London School of Hygiene & Tropical Medicine found.

Temperatures hit 35.1C in West London in May and following three consecutive days of record-breaking temperatures, highs of 37.7C on 26 June at Lingwood, Norfolk were recorded amid numerous red health heat alerts across England.

The heatwaves forced several hospitals to declare critical incidents and London Ambulance Service faced its busiest day on record with significantly more life-threatening emergency calls.

But the UK is now regularly experiencing temperatures beyond historical norms, researchers said,

“It’s time we woke up to the fact that we now live in a country with dangerously hot summers. To protect people during future extremes, we must urgently adapt to the reality of the climate we now have, and double down on global efforts to reach net zero emissions to stop this from getting worse,” Dr Clair Barnes, research associate in extreme weather and climate change, Imperial College London said.

For the study, researchers used a statistical model which uses historical records to show how the risk of dying due to elevated heat changes with temperature in each of around 35,000 very small regions across England and Wales.

This allowed the experts to estimate the number of heat related excess deaths that are likely to have happened during these recent heatwaves, using recorded temperatures.

Researchers then factored in how much the UK has warmed due to human-caused climate change and used the data to estimate how many excess deaths would have been expected if the heatwaves had occurred in a world without human-caused climate change.

Modelling suggests that from May 21-29, there were around 550 heat-related excess deaths across England and Wales and about 330 of those would not have occurred in a world without climate change – accounting for around 60 per cent of the deaths.

Similarly, during the second heatwave between June 18-28, estimates suggest there were almost 22,000 heat related excess deaths. But about 800 (40 per cent) of those deaths would not have occurred in a world without climate change, according to analysis.

In comparison, estimates for summer 2025 suggest there were 1,504 heat-related deaths, according to the UK Health Security Agency (UKHSA).

It comes as the third heatwave of the year hits the UK, with temperatures yet again exceeding 34C.

The forecasting agency said it makes 2026 a record year for the most days to reach 34C or higher in a calendar year. It beats the previous record of seven days set in both the summer of 1976 and 2020.

The World Health Organization (WHO) has recommended that authorities in Europe plan for extreme heat in the same way they do for winter flu and study authors have suggested heat deaths could eventually match the rate of deaths during the winter months.

“More deaths do happen when it is cold, but they’re not necessarily directly linked to the cold, they are often flu deaths. Whereas we see a direct link between spikes in heat and spikes in mortality,” Dr Barnes said.

Dr Ross Thomson from UKHSA added: “Heat seems to be increasing at a higher rate than perhaps the cold is, we might get to a point where our summer heat excess deaths are actually at a level of cold excess deaths, which is unprecedented.”

The Environment Agency has described heat as the largest and most urgent climate hazard for human health. It increases the risk of heart attack, stroke, lung problems as well as death from drowning.

“Heatwaves can be fatal because of the strain placed on the heart and other organs”, said Jess Beagley, policy lead at the Global Climate and Health Alliance told the Independent: “High temperatures present a particular risk for people with existing health conditions including cardiovascular diseases, as well as on babies as they are less able to regulate their body temperature, and outdoor workers as they are most exposed.”

Ms Beagley stressed the UK is not prepared for hotter summers. Homes and hospitals do not protect the public from high temperatures and we need better insulation, natural shading and air conditioning.

“We must also remember that the increasing severity of heatwaves is primarily driven by the burning of fossil fuels – there are limits to how much we can adapt to heat and other climate impacts so it’s vital that we transition from fossil fuels to renewable energy, or hazards will continue to increase,” she added.

However, people do not just die from heatstroke, the bulk of people suffer from strokes, heart attacks and sudden cardiac death, Hugh Montgomery professor of intensive care medicine, University College London explained.

However, he stressed climate change can kill people in other ways, including crop failures from drought and flooding, which causes food prices to increase affecting the most vulnerable.

“We are now in a death spiral,” the expert on health and climate change told the Independent, stressing that we need to stop burning fossil fuels: “It takes 400,000 years to fully clear the CO2 we emit today, so if everyone stopped emitting, these are still the foothills of catastrophe. That coupled with impacts on food, power, transport and natural ecosystems, could cause civil unrest,” he added.