Temperature starts in the head

People perceive heat and cold differently. This is because the brain doesn’t measure degrees Celsius, but rather how the weather feels to us.

The thermometer reads 26 degrees. ‘Pleasant,’ think some; at last it’s cooler, the heatwave is over. ‘Actually a bit cold,’ say others, because their ‘operating temperature’ starts at 30 degrees and they experience heatwaves as lovely summer days.

Who’s right? Both – neither is imagining things. That’s because between the thermometer and reality lies the brain, which can turn the same temperature into a slightly different experience for each person. Some people are born to chill out, whilst others are built for the dog days of summer.

How is that possible? The skin measures how warm it is. Thousands of thermoreceptors all over the body detect heat or cold and send these signals via the spinal cord to the brain. There, a region called the hypothalamus (see Info and Sources) controls our perception of temperature. The hypothalamus processes the signals coming from the skin and compares them with the temperature of the blood inside the body, as if it were asking: ‘How warm is the body really – and how warm should it be?’ Depending on whether we are too hot or not, it determines the body’s response.

How the body cools itself

When the body gets too hot, thermoregulation kicks in. The brain lowers blood pressure and dilates the blood vessels so that blood can flow to the body’s extremities, cool down there, and return to the heart at the correct temperature. If that isn’t enough, we sweat. The aim of these reactions is to maintain a constant normal body temperature, which in humans averages between 36.4 and 37.4 degrees.

“In doing so, thermoregulation competes with the circulatory system. This is because the circulatory system’s purpose is to keep blood pressure high, so that our lifeblood flows back to the heart and the heart can beat. In everyday life, therefore, the body’s priority is normally to ensure a steady blood pressure so that everything functions properly. However, thermoregulation must lower blood pressure to counteract the heat,” says Andreas Rössler, Professor of Physiology at the Medical University of Graz, speaking to the WZ. If it cannot carry out its work quickly enough – for example, because the blood vessels do not dilate fast enough – the body can overheat. And if thermoregulation reacts too strongly, in other words, lowers blood pressure too much, this can lead to circulatory collapse.

In extreme heat, therefore, this balance can be disrupted. Physical fitness, the fitness of the cardiovascular system, pre-existing conditions such as diabetes or obesity, as well as deposits in the blood vessels or smoking, all play a role in determining how quickly the blood vessels can dilate to bring about the desired cooling, or how quickly the balance can be upset.

The difference between ‘Born to Chill’ and ‘Feel the Heat’ types stems from an innate, personal threshold for overheating. Every person has a threshold in the brain at which they begin to regulate their body temperature. This point, at which we start to feel too hot, varies. Just as people have different blood pressure readings, absorb and process food and fluids differently, or sleep better or worse, they also have different perceptions of temperature. “This applies to many parameters of homeostasis, which ensures a constant internal environment. The hypothalamus ensures that the body maintains the set points we are born with,” says Rössler. In other words: the body is programmed to determine how long we can tolerate deviations from our set points.

‘We are tropical creatures’

When the temperature threshold is exceeded, certain proteins on the nerve cells – known as TRP proteins – warn of the higher temperatures by signalling pain to the brain. They also signal the cells to produce certain heat-shock proteins, which, like an emergency service, prevent heat-induced damage to other proteins in the body. Research is currently focusing on the specific types of TRP proteins a person possesses. In animal studies, some genetic variants of TRP have been shown to trigger a pain response even at lower temperatures. And that, in turn, could be one reason why people who carry these genetic variants find temperatures as low as 26 degrees uncomfortable.

Fortunately, we are not entirely at the mercy of our genes. The hypothalamus is responsible not only for maintaining the body’s internal environment, but also for adapting to external conditions. For example, by activating the sweat glands or even forming new ones, thereby increasing their density and improving their distribution. After all, sweating cools us down. However, this only works as long as we do not notice the sweat, because it can then evaporate. As soon as the sweat starts running down our bodies, the cooling effect is lost. By then at the latest, we realise that we should have switched on the air conditioning or moved to a different location.

If we stay in a hot climate for several weeks or move there, the sweat glands adapt. We sweat more quickly and profusely, whilst losing less salt. The blood plasma changes, and salt and water reserves build up in the skin. Furthermore, over time, new blood vessels form directly under the skin, which facilitate heat dissipation. And, as you may have noticed when travelling to the south: in the heat, you move more slowly, take breaks and sit down more often.

We can actually adapt to heat more easily than to cold, says physiologist Rössler. “We are, if you like, tropical creatures.” This ability to cope with the tropics can even be actively trained. Heat training includes regular sauna visits, cardio workouts and spending time in hot, humid environments.

Not purely a question of willpower

Metabolism, hormones, aging and gender, as well as humidity, wind, stress and medication, all influence how well we cope with the heat. For example, some antidepressants affect the release of the hormone vasopressin, which counteracts overheating: People taking such medication find it harder to tolerate heat. Other active pharmaceutical ingredients, in turn, are metabolised differently at high temperatures than usual and are therefore tolerated differently. We also feel hot more quickly when under stress; as we age, our blood vessels dilate less effectively; and women generally do not tolerate heat as well as men.

Whether we feel the cold more easily or tolerate heat better is therefore not purely a question of willpower. Many factors influence how efficiently we release heat and how quickly we sweat. It is only the interplay of genes, the brain, the environment and behaviour that turns the figure on the thermometer into a personal experience, which in the vast majority of cases is accurate.

Source: Eva Stanzl, Wiener Zeitung, 2 July 2026