WeeklyWorker

27.08.2026
Treating a victim of heatstroke in Louisiana

Heatwaves and excess deaths

Our bodies themselves are sending a clear message: something must be done about global warming as a matter of urgency. Already, reports James Linney, many thousands - perhaps millions - are needlessly dying

For us northern hemisphere dwellers, a blisteringly hot and exceedingly dry summer is coming to an end. Here in the UK, we have witnessed the familiar lush-green colours of summer being completely transformed into an alarmingly bleached yellow, until only in the past week we have had some much-needed rain.

The UK and western Europe certainly have had their hottest ever June and July.1 The UK experienced its highest temperatures (38.8°C) on August 13 - our fifth hottest day of all time - and also had its hottest June since records began back in 1916. This summer has seen a record five separate heatwaves and it is not over yet - a sixth is forecast for September. More than two-thirds of England and the entirety of Wales are officially in a drought.

Things have been even more torrid in western and southern Europe, where in parts of France, Spain and Portugal, temperatures have regularly breached 40°C; and where devastating wildfires, blown by hot, dry winds, have spread at enormous speeds. The combination of blistering heat, lightning storms igniting flash fires, and hundreds of acres of tinder-dry vegetation and farming land has been the stuff of nightmares. In France hundreds of thousands of people have had to flee their homes, as fires burned across more than 116,000 acres, where a national emergency was called and the military had to be drafted in to help the desperately overstretched firefighters. The wildfires that have raged since July have only just come under control.

The heat and fires have been deadly not just for those exposed to the highest temperatures, dying from heatstroke or from being incinerated by the flames, but for the wider population of Europe too. Statistics reveal a startling rise in the number of excess deaths from heat this summer (‘excess deaths’ is a statistical estimate rather than a direct count, estimating the number of people who died during a hot period above the expected average for that same time of year in comparable years). Between May and June England saw nearly 2,900 excess deaths,2 and this is likely to have increased even more in the hotter months of July and August. In Europe between mid-July and mid-August, more than 32,000 excess deaths were estimated.

Effects

Before we consider how the heatwaves are causing so many deaths, it will be useful to look at how heat affects us and how bodies have evolved to deal with it. If we become too hot and measures are not taken to cool us, we can become ill within a couple of hours: initially we start feeling flushed, thirsty, sweaty, fatigued and can get a severe headache. These symptoms are signs of heat exhaustion, which is like a warning system, alerting us to take action before it is too late. If the heat persists and no action is taken, we can quickly become severely ill - meaning that vomiting, dizziness, confusion, hot and dry skin, fainting, breathlessness, a racing pulse and seizures will result. This is termed ‘heat stroke’ and is extremely serious, with a mortality rate of 80%.

However, humans live in extreme environments, ranging from lows of -71.2°C in permanently inhabited Siberian villages to highs exceeding 50°C in desert regions: eg, the Danakil Depression in Ethiopia. This is possible because our body has an amazing ability to adapt to extreme temperature changes - a process called homeostasis, which maintains a fairly stable core body temperature of between 36 and 37.5°C.

Thankfully then, death from heatstroke is still unusual, even when outside temperatures surge above 45°C. This maintaining of a fairly narrow internal temperature is vital to allow an optimal environment for the millions of orchestrated chemical reactions constantly taking place inside us. Too low a temperature and these reactions slow down and eventually stop - resulting in death from hypothermia. Alternatively, as the temperature increases, these reactions speed up - this can lead to stress on our body, putting our organs and circulatory system under strain. If the internal temperature goes above 44°C, proteins eventually break down - like an egg being put into hot water, our blood and internal fluids congeal and solidify.

Humans have evolved two primary cooling systems when temperatures increase: increasing blood flow near to the skin’s surface, and sweating. In his book, Extreme survival,3 Dr Kenneth Kamler describes our skin as acting like a “car radiator”; blood (our liquid coolant) flows through our engine (organs), absorbing heat, then carries it to the skin’s surface, where the outside air helps to cool it. With increasing temperature our bodies can respond by diverting more blood to those arteries nearer the skin surface (vasodilatation) - hence, when we get hot, we look flushed and our heart rate increases.

But this system becomes less effective, the higher the outside temperature - hence the need for sweating. Our skin is covered with more than three million sweat glands, largely grouped in our armpits, scalp, chest and back. When needed, these glands are turned on like taps, allowing a layer of water onto our bodies, which is then heated by the hot outside air and evaporates - a process that transfers heat from our body to the air. This evaporation process relies on air being drier than our bodies, hence why sweating is less helpful in cooling us down in very humid conditions. In high temperatures sweating is crucial to stay alive, but the debt paid is the loss of water and salt - that is why we need to increase our water and electrolyte intake to prevent dehydration and kidney failure.

The human body then is very efficient at keeping us alive, even in very high outside temperatures, as long as we have plenty of water (and food) and can rest, ideally in the shade, (exercising in extreme heat is doubly dangerous, because contracting muscles create even more heat - like cranking the heating up on a hot day). So this leads us to the question then: why, given these adaptions, does heat lead to so many thousands of excess deaths?

The answer is due to indirect causality. Heat, as we have seen, increases the speed of the body’s chemical reactions, increasing the heart rate and leading to dehydration; hence blood thickens and our organs are put under stress. Some people are at increased risk of these stress effects. Very young, old or pregnant people are more vulnerable because their systems are less efficient at losing heat. Similarly people with chronic health conditions, such as respiratory conditions, diabetes, cardiovascular or kidney disease, are less able to deal with heat stress - which can lead to fatal exacerbations of their chronic illness, heart attacks, strokes or renal failure.

According to a new study in the Lancet Planetary Health journal, we have been greatly underestimating heat effects on older people, finding that the impact of even a rise of 1.5°C above preindustrial levels will have a detrimental impact on the health of people over 60 years old.4 Given the UK’s ageing population, this could have disastrous consequences for a national health service already unable to manage demand. According to the latest NHS statistics, emergency departments across England recorded 2.4 million attendances in June - the second-highest monthly total ever.5 An already severely overstretched NHS is now going to have to deal with both a winter and summer pressures crisis.

Underestimate

Globally, heat stress is the leading cause of weather-related death, officially killing around 489,000 people a year, but this is certainly a huge underestimate, due to the fact that heat is often not recorded as a contributing cause of people’s deaths. This is more likely to be the case in the global south, where the burden of excessive heat is felt the most, but where underdeveloped health services have less resources. In India, for example, the highest populated country in the world (1.47 billion), a large proportion of the working population are employed in manual outdoor work, exposed to the increasing high temperatures, and live in poor-quality homes, often constructed from heat-conducting materials, such as concrete and corrugated sheet metal. This year temperatures have risen as high as 48°C and, on one day in April, the world’s 50 hottest cities were all in India.6 Despite this, official statistics only attributed 84 deaths to heat in 2025, compared to 175,000 heat deaths per year recorded in Europe.

Heat and its effect on people has not been the only deadly consequence of the heatwaves this year. As wildfires have surged through multiple countries, people are increasingly being exposed to smoke and toxic air pollution. Wildfire smoke can be blown huge distances and can impact the health of people living thousands of miles away. In Canada, which has also experienced its worst wildfire season ever, with more than three million hectares being burnt, wildfire smoke in Ontario and the Northwest Territories led to 120 million people, along with those in the USA, being exposed to poisonous air.

Wildfire smoke is a collection of toxic gases and fine particulate matter (known as PM2.5) - released when vegetation, buildings and other materials burn; these cause inflammation of the airways, but can also enter the bloodstream, leading to multi-organ damage and long-lasting health effects. Like excessive heat, the same groups of vulnerable people listed above are more susceptible to these harmful effects from smoke. A recent Lancet study7 found that globally a staggering 1.53 million people a year (between 2000 and 2019) died as result of the air pollution caused by wildfires.

This summer the deadly effects of climate change have well and truly arrived in Europe and North America, but they are not exactly new, having been around for decades already. It is just that the majority of deaths have been experienced by the most poor in the global south - of little concern for the ruling class in the capitalistically advanced countries, which has, of course, always seen death among the poorest as an acceptable collateral damage for the sake of generating economic growth and therefore profits.

But the wildfires ravaging large parts of Europe this summer act as a reminder of the vulnerability of even the more economically advanced countries, meaning that ultimately our science, technology and infrastructure can be swept aside (or incinerated) in the face of the devastating power of nature being unleashed by capitalism’s abuse of our planet.

Despite this the capitalist establishment still, of course, gives preference to profit and market growth over any meaningful attempts at change. At best we get empty liberal promises to reduce carbon emissions at some point in the future; at worse blatant denial and disdain for any attempt to prevent the global climate crisis. This was evident in the interview given by Richard Tice of Reform UK recently, when he said the UK should not focus on the “doom and gloom” and instead “enjoy it when it gets warm”.8 For those wedded to the destructive drive for profit and ever-expanding markets it remains easier (or preferable) to imagine the end of the world than to consider ending capitalism.

This summer is still just the beginning - a warning of more to come - and, as with the internal homeostatic warning systems our bodies have, if ignored, disaster looms. Profound systemic social change, led by an organised working class, is of immediate and urgent importance. Without this the future looks bleak and almost too hard to contemplate.

  1. www.france24.com/en/europe/20260810-western-europe-saw-hottest-june-july-on-record-as-climate-change-fuels-historic-summer; and www.metoffice.gov.uk/blog/2026/warmest-uk-summer-on-record-increasingly-likely-as-temperatures-stay-well-above-average.↩︎

  2. www.bmj.com/content/394/bmj-2026-100452.↩︎

  3. K Kamler Surviving the extremes: what happens to the body and mind at the limits of human endurance London 2004.↩︎

  4. www.thelancet.com/journals/lanplh/article/PIIS2542-5196(26)00067-7/fulltext.↩︎

  5. www.nationalhealthexecutive.com/articles/nhs-under-strain-heatwaves-expose-corridor-care-crisis-warns-rcp.↩︎

  6. www.theguardian.com/world/2026/jul/29/extreme-heat-deaths-india-climate-crisis-environment.↩︎

  7. www.thelancet.com/journals/lancet/article/PIIS0140-6736(24)02251-7/abstract.↩︎

  8. www.thelondoneconomic.com/politics/richard-tice-climate-change-comments-409112.↩︎