Heat or cold: What influences our comfortable temperature

38 degrees Celsius in the shade – for some people, the ideal temperature to enjoy summer to the fullest. For others, it's a sweaty nightmare, associated with headaches and respiratory and circulatory problems. Instead of the heat, this group wants a jacket-friendly 13 degrees Celsius, or even wintery subzero temperatures.

Everyone has their own comfortable temperature. But what determines it?

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There are more than 60 factors that influence thermal well-being, explains Andreas Matzarakis, a biological and environmental meteorologist at the Albert Ludwig University of Freiburg. These influencing factors include:

• Age : Older people have a slower metabolism than younger people, as well as thinner skin and less muscle mass. This makes them generally colder.
• General health : A healthy body can regulate temperature better. However, people with chronic diseases such as multiple sclerosis are often more sensitive to heat and cold than healthy people.
• Hormone balance : The male sex hormone testosterone promotes muscle growth, which is associated with greater heat production. Therefore, men generally don't get cold as quickly as women.
• Stress : Stress hormones constrict the blood vessels, which leads to an increased sensation of cold.
• Clothing : What clothing someone wears at certain temperatures determines whether he or she is more likely to sweat or freeze.
• Environmental and weather conditions : In high humidity, the body has difficulty cooling down because cooling sweat from the skin evaporates more slowly. The air is perceived as warmer. Wind also influences the perception of temperature, as does sunlight.

The human body has a certain "operating temperature," as Matzarakis puts it. It's around 37 degrees Celsius. "This temperature is optimal for many biochemical processes in the body," says the biometeorologist. Anything above that can quickly become dangerous for the body. It can lead to cardiovascular problems, for example. "This means the core temperature must not deviate too much from 37 degrees." A comfortable room temperature, at which the body has little to do to maintain heat, is between 18, 19, and 25 degrees.

Normally, the body tries to cool itself in high temperatures – through sweat. This evaporates from the skin, cooling the body. This is known as evaporative cooling. If this regulatory mechanism is disrupted – for example, because the humidity is too high and sweat has difficulty evaporating – additional help is needed. Physical activity should be reduced and shady areas sought.

The body reacts differently to cold: First, the blood vessels constrict to reduce heat loss. Extremities like the hands and feet become cold; all heat stays in the core of the body to preserve vital organs like the liver, lungs, brain, and heart. Goosebumps are also typical of a sensation of cold: the hairs on the skin stand on end to create an insulating cushion of air against the cold. You also begin to shiver. Your muscles contract and relax – thus generating heat.

How we perceive temperature is also determined by our brain. It has a "thermal cortex," a region of the brain responsible for processing temperature stimuli, as a research team at the Max Delbrück Center for Molecular Medicine in Berlin discovered in 2023. Furthermore, the brain can adapt to different temperatures, so the perception of heat or cold can vary over time.

Biometeorologist Matzarakis gives the example: When summer transitions into autumn, our bodies are still accustomed to warmth. 28 degrees Celsius in September might therefore seem perfectly normal; even at lower temperatures, we still reach for our cardigan. After winter, the body is more accustomed to cold. The brain therefore anticipates how a temperature should feel based on previous experiences and adapts accordingly.

Getting your body used to temperatures you find uncomfortable is only possible to a limited extent, says Matzarakis. Cold therapies, for example, can help the body cope better with low temperatures. Getting used to high temperatures is more difficult, says the expert. In general, it helps to harden your body so it can better cope with temperature fluctuations. "This works best with exercise in the fresh air—it's not about jogging or extreme sports, but simply walking," says Matzarakis. "Contrast showers and Kneipp baths can also help with hardening."