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WEATHER

Why do temperatures of 25C feel so hot in Denmark?

A temperature of 25C (77F) is hot enough to qualify as a heatwave in Denmark but seen as an average summer’s day in other parts of the world. Why do Danes feel the heat more, and what can be done to mitigate the effect of heatwaves in the future?

Why do temperatures of 25C feel so hot in Denmark?
People in Copenhagen try to keep cool during a heatwave in 2023. Photo: Mads Claus Rasmussen/Ritzau Scanpix

Although most of June 2024 was cool, this week has seen the summer begin to heat up with temperatures at or close to 25 degrees Celsius on several days.

For readers from a lot of other countries, this might not feel like a big deal, but in Denmark, it’s warm.

There is no standard international definition of a heatwave, with each country deciding how to define it, but Denmark’s definitions underline the fact that 25 degrees is generally seen as uncomfortable.

Denmark’s national meteorological agency, DMI, defines a heatwave or varmebølge as a three-day period on which the average highest temperature is over 25 degrees Celsius.

There’s also an additional ‘level’ of heat wave, hedebølge, for which the average highest temperature for the three days in question must exceed 28 degrees Celsius.

READ ALSO: Danish word of the day: Varmebølge

Danes in general are more used to cold temperatures and the country’s infrastructure is built with this in mind.

A 2023 report from Oxford University placed Denmark among the countries which are the most poorly prepared for increasing global temperatures.

That is due in no small part to the construction of Denmark’s buildings, which historically has been with a different climate in mind to the one considered in the report — essentially, Danish buildings are generally designed to keep heat in and with cooling a lower priority.

READ ALSO: Why hot weather feels even hotter in Danish buildings 

It’s an issue which doesn’t affect Denmark alone but all of the Nordic countries.

Engineering consultancy company Sweco recently investigated how a number of different European cities, including Copenhagen, could build heatwave resilience as climate change looks likely to increase their frequency. In Copenhagen, the number of heatwave days per year is expected to increase by 160 percent by 2100, with similar figures for the other Scandinavian capitals Stockholm (150 percent) and Oslo (140 percent).

“The increase in temperature is greater here [in the Nordic countries] and we have probably come the least far in planning for it. We’ve been more focused on protecting ourselves from the cold,” Martina Söderström, division manager with  Sweco Environment & Planning, told The Local Sweden.

 “If you look at Rotterdam and Brussels, for example, they’re further ahead both in measuring the heat and maybe also have a clearer plan of the measures they’re going to take to mitigate it.”

Denmark also has a lot of sunlight during the summer – Copenhagen gets over 17.5 hours of sunshine around midsummer, while Aalborg in the north gets 18 hours.

This means that temperatures often stay high during the night, providing fewer opportunities for people to recuperate from the heat and putting more stress on vulnerable individuals.

Söderström said that there are ways of mitigating the problem, with city design central to this.

“Natural solutions are an important piece of the puzzle,” Söderström said. 

“It’s important to get green and blue infrastructure into city planning. Trees are great, as they give shade and also they release water vapour into the air which has a cooling effect, and bodies of water can have the same cooling effect – when it’s cooler than the surrounding air, it helps to cool it down. So water, green solutions, proximity to parks and shade, all of those things are important to have in a city environment.”

People in cities are also more affected by heatwaves, Söderström added, as hard surfaces like asphalt, concrete and metal roofs absorb heat, further warming the air as this heat is emitted.

“It’s important to think about this when planning areas. Think about getting plants and water into urban areas, but also the materials being used.”

Do you come from somewhere with a warmer climate than Denmark? How do you find the heat here? Does it affect you more or less than it did back home? Let us know in the comments below.

Member comments

  1. If you want to feel better about the temperature, try Texas for a few hours. Today in Dallas it’s 101 f with a heat index of 112. Fortunately I expect to be in Denmark next week.👍🇩🇰😀

  2. Why you didn’t mention that the actual feel of the heat is higher because of the higher air humidity? Simple. That is the main reason why it feels hotter than in dryer conditions in other cities.

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WEATHER

‘I get more sunburnt’: How foreigners cope with Scandinavian heatwaves

Temperatures have recently hit levels defined as ‘heatwave’ in Scandinavia, so we asked our readers in Norway, Sweden and Denmark how they cope with Nordic summers.

'I get more sunburnt': How foreigners cope with Scandinavian heatwaves

A temperature of 25C (77F) might not feel like a big deal in many countries, but in Scandinavia, it’s warm.

While Scandinavians are generally used to colder temperatures, there’s more to it than this: The way cities and buildings are designed — to retain heat rather than keep cool — goes some way to explaining why temperatures that feel like a regular summer day elsewhere seem so severe in the Nordics.

READ ALSO: Why are temperatures of 25C considered a heatwave in Sweden?

How do you get on with Nordic heatwaves?

“I get more sunburnt here due to the lack of humidity and dry weather,” wrote Zaki in Stockholm, who said that he had been used to similar temperatures but more humid conditions before living in Sweden.

Zaki’s experience isn’t unique.

“Gothenburg heat roasts me (give me slight burns) and wind cools it down quite often,” an anonymous reader stated. They described the climate in their home region of India as “hot and humid”.

Although Scandinavian summers can be hard going for some, they are a piece of cake for others.

“25C is not a heat wave. 45C and above is,” as Rajan from India put it.

Mohammed, an Egyptian who moved to Stockholm three years ago, says hot Swedish weather “encourages me to engage in more outdoor activities”.

“My country is much hotter, drier, and more humid (landscape is +90% desert). Population density is extremely heavier, and urban areas tend to be jammed by diesel-fueled vehicles, which usually turn on AC, which in turn contributes to more heat,” he explained.

Thomas, a US national who lives in Uppsala, said “summers are great here, even on the hottest days.”

“Humidity is low here and if you’ve experienced a 30+ degree day with high humidity, as I did often in the Southern and even Eastern US, you certainly will count your blessings to be in Sweden during the summer,” he said.

Another American reader, Chad from Texas, did say that Nordic heatwaves are “much worse when it happens with lack of air conditioning and having highly heat insulated home”.

Texas has “essentially the opposite climate. However, Dallas is fairly low humidity,” he said.

An anonymous reader who is Swedish but has lived in southeast Asia said that Sweden’s hot weather “affects me much more!”

“I am struggling when the weather is 25C or above,” he said.

When in southeast Asia, “the building is cooler, and also since the sunlight only lasts for 12 hours or so, it did not retain the heat from previous days,” he explained.

“It affects me more because people here are out and about when it’s 28C to 30C but back home, we’d rather stay at home/inside the mall with AC/hang out in coffee shops or restaurants with AC, but here AC is not so common,” wrote a reader from the Phillippines.

What can Scandinavia learn from warmer countries?

One key difference between Scandinavian building designs and those in warmer countries is a lack of air conditioning. While this would effectively cool buildings in hot weather, it would also consume more energy – something which would concern countries such as Denmark, which have politically-determined emissions targets.

“I don’t think we should introduce A/C here [in Denmark, ed.], so nothing in particular to learn. Just have lots of sunscreen and shade trees,” said a reader who moved from New York City to Odense.

Other appliances can also be used for cooling, however – and these are also rare in Scandinavia.

“Majority have ceiling fans at home which we use religiously. People of middle class and above also have air conditioners in their bedrooms,” Zaki said.

Hydration strategies also make a difference.

“Have lots of lime juice and lukewarm water. Avoid ice-cold water due to frequent change in weather. If you sweat a lot, make sure to have salty foods to balance your body,” the Gothenburg-based reader from India wrote.

“Air Conditioning and drink coconut water, Lassi with salt etc.”, recommended Rajan, also from India.

In Egypt, “we just use AC and ceiling- or stand-fans. We also have to take several cold showers during power outages,” Mohammed said.

“Chilled drinks and fruits (especially watermelons & muskmelons) can never be resisted,” he added.

“Not really sure if Scandinavia can learn anything from my country, but I guess fans might be a more environmentally-friendly (still a very effective) option than AC,” he said.

Some readers who are acclimatised to hot climates felt few adaptations are needed in the Nordics.

“Most I do is put on a short sleeve shirt. I turn on some fans in my apartment and make sure to keep the windows open at night and close them when the sun is strongest,” Thomas in Uppsala said.

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