Monday, July 13, 2026 • 6:02 PM UTC - in Denmark

Heatwaves in Europe this summer have led to more deaths than during a normal summer.

This was the case, for example, in late June, when 10,000 more deaths than usual were recorded in the 27 EU countries. Over 9,000 of those deaths were among people aged 65 or older, according to data from EuroMomo, a European mortality monitoring system, as cited by Ritzau.

But how can heat kill – and what do people actually die from during a heatwave?

Heat expert Jacob Feder Piil knows all about this. He has written a PhD on temperature regulation and researches, among other things, our tolerance for heat. Here he provides the key physiological explanations.

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Demanding for the circulatory system

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When deaths occur as a result of heat, it is not because we humans cannot regulate our body temperature. In fact, we are very good at it.

However, heat still places extremely high demands on the cardiovascular system, as it needs to transport extra blood to the skin, explains Jacob Feder Piil.

"And it is especially frail and elderly people with cardiovascular problems who are vulnerable," he says.

Denmark also felt the heat in late June, when the highest temperature ever recorded in Denmark was measured. This happened on Saturday, June 27. (Photo: © Emil Nicolai Helms, Ritzau Scanpix)

"This is because we humans combat a rise in our internal core temperature by sweating, and to be able to sweat, the heat must be transported with the blood to the skin, where beads of sweat on the skin's surface evaporate into the surroundings, thus releasing the heat. If you have challenges with the cardiovascular system, and it has to work extra hard, it becomes a problem."

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Heat is stress for the body

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Jacob Feder Piil emphasizes that there can be many other physiological reasons why heat ends up being fatal.

When it is particularly hot – as during a heatwave – the temperature in our body rises, despite the body's efforts to fight it. When the body's temperature rises too much, a number of problems arise, the first of which are felt as malaise and dizziness.

From there, heatstroke follows.

Furthermore, we risk dehydration, which can lead to death.

"When we start sweating, we lose fluid from the body, and then we become dehydrated. Dehydration places greater demands on the circulatory system and the brain, and it becomes difficult to regulate our temperature because we cannot produce sweat," says Jacob Feder Piil.

He points out that this can especially apply if you forget to drink enough.

"A heatstroke typically creeps up slowly and quietly, but once it sets in, and if you are not cooled down quickly and have your fluid replaced, you can die from it within a short time," says Jacob Feder Piil.

All of this is particularly challenging for the sick, frail, and elderly, who may already have issues with their cardiovascular system, as the heart has to work at high pressure. This is less of a problem for healthy and fit people in good physical shape, explains Jacob Feder Piil.

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What you can do yourself

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* Seek shade.

* Drink plenty of fluids.

* Wear light clothing that helps you release heat.

* Keep an eye on your urine. Dark urine is a sign of dehydration; it should be light yellow, and you should ideally urinate several times a day.

* Additionally, it can be beneficial to do as little as possible and stay in a temperate climate if possible. This is because physical activity increases heat production in the body, meaning you need to get rid of even more heat.

Source: Jacob Feder Piil

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Let the sweat evaporate

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According to Jacob Feder Piil, you can often feel in your body that something is brewing.

"The first thing that happens is dizziness. You get a headache; that is a pretty strong sign. You can also keep an eye on your urine; it should be light yellow. If it is dark yellow, it is a strong indicator of dehydration. You should ideally urinate several times a day."

There are several factors we can pay attention to ourselves to stay as safe as possible during extreme heat. Among other things, Jacob Feder Piil recommends that we avoid wiping away all the sweat constantly, unless it is running down and bothering your eyes.

"Sweat should ideally evaporate from the skin. It is hard to understand that sweat can evaporate into the surroundings, but it can. When sweat evaporates from the skin, it cools us down because the heat in the body is transferred to the surroundings."

Jacob Feder Piil says this can also happen by touching something cold – for example, dipping in water or letting a cold wind blow across the skin.

"You can place your hand on a cold surface or stick your forearms in cold water. This releases heat very quickly."

According to Jacob Feder Piil, it is therefore not entirely stupid – solely from a heat regulation perspective – when you see people jumping into a fountain during heatwaves.

"It is extremely effective to jump into cold water, because water's conductivity is enormously good compared to air. For elderly people in nursing homes, it can therefore be beneficial to sit in a chair with their legs in a wading pool during severe heat," says Jacob Feder Piil.

Also read the doctor's advice on how to stay cool when it is dangerously hot. ( https://www.dr.dk/nyheder/indland/slap-af-saadan-holder-du-dig-kold-naar-det-er-farligt-varmt )

Warning: This article was translated by a Large Language Model, in case of doubt, you can always visit the original source.