Extreme heat: is the UK becoming a 40C country?

Summary

Science Weekly – Episode Summary

Episode Title: Extreme heat: is the UK becoming a 40C country?
Release Date: June 23, 2026
Host: Ian Sample, Science Editor, The Guardian
Guest: Ajit Naranjan, Europe Environment Correspondent, The Guardian

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Overview

This episode of Science Weekly examines the unprecedented heatwave gripping the UK and Europe, exploring what’s causing record-breaking temperatures, the role of climate change and El Niño, and urgent steps societies and individuals can take to adapt to this new climate reality. Ian Sample and Ajit Naranjan discuss whether 40°C is becoming the new normal for the UK, the health and societal impacts of extreme heat, and practical measures to mitigate risks.

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Key Discussion Points & Insights

1. Record-Breaking Heatwaves in Europe and the UK

• The UK is experiencing an intense heatwave, with the possibility of matching or beating its all-time record of 40°C (02:01–03:33).

• France, Spain, and Italy are also facing severe heat; France has placed about a third of the country on red alert, forced school closures, and banned public alcohol consumption (02:26–02:45).

• For the UK, this represents an extraordinary deviation from historic averages, as June’s previous record (35.6°C) is now 2–3 degrees lower than current forecasts (03:33).

  “The UK really is just not [used to these temperatures]... the temperature record for June is just 35.6 degrees Celsius, which is a full 2 to 3 degrees lower than what we're about to see this week.”
  — Ajit Naranjan (03:33)

• High humidity also means people will experience “tropical nights,” when temperatures stay above 20°C, preventing recovery from daytime stress (03:33).

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2. Causes of the Current Heatwave and the Role of Climate Change

• Immediate cause: a massive “heat dome” (area of high pressure) acts as an “atmospheric lid,” blocking cloud formation and baking the region (04:31–05:17).

• Underlying driver: Climate change from fossil fuel emissions has increased Earth’s average temperature by about 1.3°C since the Industrial Revolution, a trend that shows no signs of stopping (04:31–05:17).

  “Both I and probably every single climate scientist you ever speak to will sound like a broken record here. It is because we burn fossil fuels that spew gas that trap sunlight and heat the planet.”
  — Ajit Naranjan (04:31)

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3. The El Niño Factor: What’s Godzilla Got to Do With It?

• A new El Niño event is beginning to form; although not directly responsible for the current heatwave, it is expected to peak towards the end of the year and could make 2027 the hottest year on record (05:17–07:15).

• The so-called “Godzilla El Niño” could exacerbate global temperature records and multiply the effects of existing socioeconomic crises, like high energy prices and food insecurity worsened by geopolitical events (05:33).

  “In El Nino years... you end up with this quite toxic mix of different factors that basically mean a lot of people who are worried about food security have started to say, hey, this is actually a kind of a looming disaster.”
  — Ajit Naranjan (06:51)

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4. Is the UK Becoming a 40°C Country?

• 40°C was once unthinkable in the UK, but recent and upcoming years are expected to regularly hit or surpass this milestone, making it a “new normal” (07:21–08:39).

• The UK’s temperature perception has dramatically shifted in just the past decade or two, with more heat records expected, especially during July and August (07:39).

  “The 40 degree temperature mark was crossed in the UK for the first time... these sorts of temperatures were not things that people were discussing [15 years ago].”
  — Ajit Naranjan (07:39)

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5. Health Impacts of Extreme Heat

• Heatwaves profoundly stress the human body — from dehydration and heatstroke in vulnerable groups (e.g., people working outdoors, homeless populations) to increased deaths among the elderly and chronically ill (08:45–10:25).

• Tropical nights compound risks by denying people the recovery time normally afforded by cooler nights.

• Most heatwave deaths occur “out of sight” in private homes among vulnerable people, and many could be prevented with better awareness and support (08:45–10:25).

  “The bulk of these deaths are happening out of sight. Perhaps a grandparent, perhaps an older relative...people who are not expected to die within the following six months or so. So it is a considerable amount of life that is being lost as a result of these heat waves.”
  — Ajit Naranjan (09:38)

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6. Societal & Economic Impacts

• Heatwaves disrupt infrastructure:

  • Energy generation is hit as hydropower dams and nuclear plants struggle with water shortages.
  • Agriculture suffers from drought and heat stress, especially during critical planting/harvesting periods.
  • In El Niño years, the intersection of climate impacts and supply chain/inflation issues raises risk of systemic failures (10:25–11:40).

  “When you've got high heat and you've also got drought...hydropower dams, they have less water to power economies. The nuclear power plants...also start to struggle.”
  — Ajit Naranjan (10:45)

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7. Adapting to a Fiery Future: What Can Be Done?

Government Measures

• Only 21 of 38 European countries had official heat health action plans as of 2024; robust government-led preparation is essential (13:53).

• Urban heat island effect makes cities several degrees hotter; increasing green spaces in cities (e.g., converting car parks to parks) can mitigate extreme heat (13:53–15:10).

  “If you were to turn car parks into parks with green spaces and trees, you would solve multiple issues at the same time.”
  — Ajit Naranjan (14:45)

Individual Actions

• Simple steps save lives: stay hydrated, use shade, keep windows closed if cooler inside, draw blinds (15:18).

• Critically, the most at-risk individuals are older adults living alone — checking on neighbors and relatives during heatwaves is essential:

  “Looking after the people around you who are going to be at risk is probably one of the first steps to avoiding the much more catastrophic suffering that we tend to see...”
  — Ajit Naranjan (16:16)

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Notable Quotes & Memorable Moments

• “From the perspective of today, we can look back and think, gosh, I didn't remember that when I was young. And now it seems to be happening more and more. When we're old, we're going to look back at some of these heat waves and think, oh, that was actually quite a cool year.”
  — Ajit Naranjan (08:13)

• “Some of the health experts have made the case to me... if you were to take many simple measures, you could avoid a lot of the deaths. A lot of these deaths are essentially needless suffering that could be avoided.”
  — Ajit Naranjan (15:40)

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Important Timestamps

• 02:01 – Record heatwave details announced
• 03:33 – Discussion of UK temperature records and tropical nights
• 04:31 – Heat dome explained and link to fossil fuel climate change
• 05:33 – El Niño overview and global impacts
• 07:39 – The UK's changing climate and normalization of 40°C
• 08:45 – Health impacts and “invisible” heatwave deaths
• 10:25 – Societal and infrastructure disruption
• 13:53 – Government needs for heatwave planning, urban adaptation
• 15:18 – Individual actions to prevent heat deaths
• 16:16 – Importance of community care during heatwaves

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Conclusion

This timely episode underscores that 40°C summer days are no longer science fiction for the UK and much of Europe — they’re becoming part of life. Preparation, adaptation, and community support are vital to saving lives in an increasingly overheated world. As Ajit Naranjan aptly summarizes: “Looking after the people around you who are going to be at risk is probably one of the first steps to avoiding the much more catastrophic suffering...”

Transcript

[Ajit Naranjan]

This is the Guardian.

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[Ian Sample]

Temperatures across the world are once again breaking records. In the UK this week we're expecting to have the hottest June day ever.

[Ajit Naranjan]

An intense heat wave will be developing this week affecting many parts of the uk and the UK Met Office has now issued a very rare red weather warning for extreme heat on Thursday.

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Parts of Italy, France and Spain are

[Ajit Naranjan]

facing heatwave conditions this weekend. Temperatures in northern and central regions are forecast to reach 40 plus degrees Celsius. France placed about a third of the

[Quo Advertisement Voice]

country on red alert, banned drinking alcohol

[Ajit Naranjan]

in public in some areas and ordered 845 schools to close Monday.

[Ian Sample]

And this extraordinary heat might be just the beginning of a sweltering year ahead. The latest El Nino climate event is coming our way and some scientists have nicknamed it Godzilla. But why exactly is it so hot? Could El Nino make it even worse? And how can we adapt to this new normal? I'm the Guardian Science Editor, Ian Sample, and this is Science Weekly. Ajit Naranjan you're the Guardian's Europe environment correspondent. We're just heading into what is set to be an extreme heat wave across Europe. What are we likely to see?

[Ajit Naranjan]

So the UK is set to come close to its all time record of 40 degrees Celsius this week. So temperatures will likely go as high as kind of 38, 39 degrees C. Parts of France are expected to hit temperatures even as high as 42. Spain may even surpass that. Now, all of this is kind of quite striking, partly because a of just how hot northern Europe has really become. If you think about Spain and France, maybe you're more used to these sorts of temperatures. The UK really is just not. So I think the temperature record for June is just 35.6 degrees Celsius, which is a full 2 to 3 degrees lower than what we're about to see this week. Now, because it's so humid, scientists expect that this heat is going to feel even more oppressive than it otherwise would be. And so that will come with these tropical nights. And that's when the minimum temperatures don't drop below 20 degrees Celsius. And that means you can't even properly recover from the stress of the day.

[Ian Sample]

What is behind this heat wave then? What's causing it?

[Ajit Naranjan]

So the immediate cause of this is what's called a heat dome. So this massive area of high pressure sitting over the UK and Western Europe, I saw one scientist describe it this morning as an atmospheric lid that's suppressing cloud formation and allowing this relentless sunshine to just bake the brown day after day after day. Now, why do these heat waves keep getting hotter? Both I and probably every single climate scientist you ever speak to will sound like a broken record here. It is because we burn fossil fuels that spew gas that trap sunlight and heat the planet. So temperatures at a global average level have increased by about 1.3 degrees Celsius since the Industrial Revolution. And they are predicted to just keep getting hotter and hotter.

[Ian Sample]

Ajit, you've been writing about what some people are calling the Godzilla El Nino, this global climate phenomenon where temperatures in many parts of the world are pushed up alongside extreme events like droughts and rain. Is this the start of the El Nino?

[Ajit Naranjan]

So El Nino is just beginning to form in the Pacific Ocean. We're just seeing the first signs that meteorological agencies are calling it as having returned after a few years without it. It is only expected to reach its full strength toward the end of the year and then last over into 2027. So this heat wave is essentially unrelated to anything going on over there. But the projections are that it may well be a very strong one when it peaks. And the World Meteorological Organization has cautioned that it's still a bit too early to call the strength of it. So they've kind of thrown a little bit of cold water on the projections calling it a Super El Nino or Godzilla El Nino. But that is largely because the models that they're showing still show a fairly wide range of what could happen. If you look at kind of the average of where those models are ending up, it does seem like it could be in the moderate to strong category. And all of that together makes it pretty likely that next year will end up being the hottest year on record globally. And for the heat waves that we're experiencing, that means that each one will just be pushed that extra bit hotter. In terms of the other effects that an El Nino year brings, in many ways they're coming at the worst possible time. So the Iran war has led to huge spikes in energy prices. The closure of the Strait of Hormuz means that there's less fertiliser getting out of. And then coupled with things like inflation, all the rest of it, you end up with this quite toxic mix of different factors that basically mean a lot of people who are worried about food security have started to say, hey, this is actually a kind of a looming disaster and if we don't act now to avert a crisis, then we are going to see these kind of very, very heavy knock on effect.

[Thomson Reuters Advertisement Voice]

Foreign.

[Ian Sample]

As you mentioned, in the uk we're set to beat previous temperature records set for June by about 2 degrees. I think that was set 50 years ago in 1976. But we're seeing more and more heat waves driven by the climate crisis. Are Europe and the UK becoming 40 degree countries?

[Ajit Naranjan]

Essentially, yes. I mean, I think the 40 degree temperature mark was crossed in the UK for the first time in 20. This year and the following year are very likely to be years in which more records fall, more records are broken, partly, as we just said, as a result of the El Nino, that will boost global temperatures a bit further next year. What's interesting in the UK's case is that, I mean, I think none of us would imagine 40 degrees even just 10 years ago. Fifteen years ago, these sorts of temperatures were not things that people were discussing. I think in my case, when it goes above 25 degrees, I feel a bit too hot. I don't know if, Ian, from your childhood, you remember anything even vaguely approaching a 40 degree heat wave. And we're not Even at the July, August stage, where things usually tend to be the worst. But it's always worth mentioning that from the perspective of today, we can look back and think, gosh, I didn't remember that when I was young. And now it seems to be happening more and more when we're old, we're going to look back at some of these heat waves and think, oh, that was actually quite a cool year.

[Ian Sample]

What kinds of impacts do heat waves like this have? Let's start with health impacts.

[Ajit Naranjan]

So the thing about heat waves is that they basically stress the body. All your organs start to have to work harder, your heart's pumping blood faster, your body's struggling to deal with all the different processes that it kind of completes on a regular day to day basis. And what happens is when you get this high level of heat, people often think about it as, oh, gosh, that means that I'm going to be out in the sun, I'm not going to have drunk enough water and I might get knocked down by heatstroke. That is a risk. And particularly if you're homeless, if you're working a job that requires you being outdoors, then you are definitely at quite a high risk of stuff like that happening. But what people maybe fail to grasp is that the bulk of the deaths that happen, and we're talking tens of thousands across Europe on a typical summer, the bulk of these deaths are happening out of sight. Perhaps a grandparent, perhaps an older relative, perhaps a neighborhood. People, particularly with pre existing health conditions, are basically just being stressed that little bit further to an extent that pushes them over the edge. Maybe you could cynically say some of these deaths would have happened anyway. Can you really blame it on the heat wave? In a lot of cases, these are people who are not expected to die within the following six months or so. So it is a considerable amount of life that is being lost as a result of these heat waves. And it extends down to young and fit and healthy people as well. And, and one thing we mentioned earlier, the kind of tropical nights that we're now having, these are really significant because even if you manage to kind of get through the day and you keep yourself well hydrated, you stay in the shade, you do all the things that people tell you should do. If your body can't really rest at night, then you really can't recover that well from all the stress that's kind of accumulated in your body over the course of the day.

[Ian Sample]

And what about the impact sort of more widely in society, things like transport, agriculture, infrastructure?

[Ajit Naranjan]

The problem with heat is that society tends to kind of just slightly slow down or the processes that would otherwise happen start to fall apart. So energy is a big one for this because when you've got high heat and you've also got drought, that comes with it often then hydropower dams, they have less water to kind of power economies. The nuclear power plants that require a lot of cooling also start to struggle. So you have these little ripple effects in different parts of the economy. For farmers, people know it probably best as having drought and dry land, high heat that kind of kills some of their crops, particularly when it comes to crucial times around harvesting or planting. It runs the full gamut of the economy. In El Nino years where you've got the high level of global temperature combined with these different various shocks that have been turbocharged, these extreme weather events that have been made a bit worse because of the extra heat or because of the El Nino, then you end up with these kind of often catastrophic failures where crops fail and these can trickle down into into almost society collapsing events.

[Ian Sample]

Coming up, how to stay cool in a fiery future.

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[Ian Sample]

Ajit A lot of people are gonna be wishing right now that they had aircon in their homes. And certainly compared to the Mediterranean, Northern Europe feels woefully ill prepar for the heat that's coming. What are the kinds of things that we should be doing to be prepared for future heat?

[Ajit Naranjan]

So the most boring answer that I think the scientists would stress to me is that governments need heat health action plans. And that is basically saying, have a plan for when it gets too hot. Your climate scientists can predict your weather, forecasters are telling you it's going to get hot. You as a country, as a government, as a city, you need to be able to respond. And people need to know to take precautions before the heat wave has hit. I think a survey of European countries in 2024 found that just 21 of 38 European countries had heat health action plans. That figure, I think has gone off slightly better in the last couple of years. But we're still talking just over half. Right. In terms of how a society can adapt in practice. I mean, anyone living in a city will know that it is just so uncomfortably hot when it does get hot. And this is partly related to something called the urban heat island effect, which basically means that cities and urban spaces are about a couple of degrees Celsius higher than their surroundings because you've got all of this concrete and tarmac absorbing the heat and you've got this extra activity, combustion of fuels. If you were to turn car parks into parks with green spaces and trees, you would solve multiple issues at the same time. But one of them is that you make cities better able to cope with heat waves.

[Ian Sample]

And what about on an individual level? What are the things we should be doing ourselves to cope better with a heat wave when it comes?

[Ajit Naranjan]

Yeah, so it's a good question because I think when you talk about a lot of climate related problems, there is maybe this feeling that, oh, I can't do anything. It should be the government. Why are we talking about anything other than just burning fewer fossil fuels? But the thing about heat is that it kills way more people than it should, even in relatively rich countries. Right. And one thing that some of the health experts have made the case to me on is that if you were to take many simple measures, you could avoid a lot of the deaths. A lot of these deaths are essentially needless suffering that could be avoided. And some of that can be done through quite simple individual actions. So to tick off the obvious ones, drink lots of water, stay in the shade if you can, stay indoors if you can, maybe slightly counterintuitively, but if your home is cooler than the outside, then keep your windows closed. Don't open them if you can, draw blinds if you can increase the shading. That being said, thinking about yourself is really only one part of the solution here. And that's because most of the people who are dying during a heat wave are much older. And in many countries, many rich countries, a lot of older people are living alone. And this is really probably one of the most powerful things that you can do in a heat wave, I think, is to check in on older relatives. Go knock on the door of your neighbor if maybe they're retired, maybe they're living alone, maybe one of their, their spouse has passed away and just see how they're doing. Maybe that requires you calling an ambulance, maybe it requires you just sitting with them and enjoying an ice cream. Looking after the people around you who are going to be at risk is probably one of the first steps to avoiding the much more catastrophic suffering that we tend to see when we have studies at the end of heat waves that show, okay, across an entire continent, 40, 50, 60, 70,000 people have died as a result of the heat wave.

[Ian Sample]

Tough summer ahead. By the sounds things. Ajit. Thank you.

[Ajit Naranjan]

Thank you.

[Ian Sample]

Thanks again to Ajit Naranjan. You can find all his [e-mail] that's it for today. This episode was produced by Madeline Finley. It was sound, designed by Ross Burns and the executive producer is Ellie Burey. We'll be back on Thursday. See you then.

[Ajit Naranjan]

This is the Guardian.

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[Ajit Naranjan]

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