Why 23°C Can Suddenly Feel Cold: The Science Behind Your Changing Temperature Perception
If 23°C used to feel like the perfect summer temperature but suddenly has you reaching for a jumper, you are not imagining it. The way your body experiences temperature can change significantly after a prolonged spell of warm weather.
A day that looks comfortably warm on the thermometer can feel surprisingly cool when you step outside. This can be especially noticeable in late summer, when the weather changes from hot and humid conditions to cooler, windier or wetter days.
There is a scientific explanation for this apparent contradiction. Your perception of temperature is influenced not only by the actual air temperature, but also by how your body has adapted to recent weather, as well as wind, humidity, sunlight and other environmental conditions.
Why 23°C can feel colder after a hot summer
One of the biggest reasons for the sudden chill is a process known as temperature acclimation or acclimatisation.
Your body is constantly working to maintain a stable internal temperature. It uses the brain, nervous system, blood vessels and sweat glands to respond to changes in the surrounding environment.
After spending weeks in hot weather, your body becomes accustomed to higher temperatures. A temperature that once seemed normal can therefore feel cooler when conditions suddenly change.
Research discussed by Michigan Medicine explains that the human body adapts to repeated exposure to heat. Laure Rittié, a research assistant professor of dermatology at the University of Michigan, describes this as an adaptation in which the body becomes accustomed to warmer conditions and changes the point at which cooling responses are triggered.
This helps explain a familiar seasonal experience. The same moderate temperature can feel chilly in autumn but pleasantly warm in spring.
The number on the thermometer has not changed. Your recent experience of temperature has.
Your brain plays a major role in feeling hot or cold
It is easy to assume that your skin simply detects the temperature and sends that information to the brain. In reality, temperature regulation is much more complicated.
Specialised sensory receptors detect changes in temperature, while the brain processes that information and coordinates the body's response.
When you become too warm, your body can increase blood flow to the skin and stimulate sweating. When you become cold, blood vessels can constrict and your muscles may begin to shiver, helping generate and conserve heat.
Your perception of temperature is therefore not simply a direct reading from an internal thermometer. It is the result of several physiological processes working together.
That is why two people standing in exactly the same place can have very different opinions about whether the weather is warm or cold.
Wind can make a mild day feel surprisingly chilly
Air temperature is only part of the story.
Wind can make a major difference to how cold you feel because moving air increases the rate at which heat is removed from the surface of your body.
Imagine standing outside on a calm 23°C afternoon. It might feel comfortable, particularly if the sun is shining. Now imagine the same temperature accompanied by strong, cool winds. The experience can be completely different.
The Met Office explains that moving air removes heat from the body more quickly than still air. This is the basis of the wind chill effect. Its "feels like" temperature takes factors including air temperature, wind and humidity into account to give a better indication of how conditions may actually feel outdoors.
This is particularly relevant in the UK, where a breezy summer day can feel considerably less summery than the headline temperature suggests.
Humidity changes how temperature feels
Humidity is another important factor.
Humidity refers to the amount of water vapour present in the air. It affects how efficiently sweat can evaporate from your skin.
When humidity is high, sweat evaporates more slowly. Because evaporation is one of the body's main cooling mechanisms, humid weather can make warm temperatures feel hotter and more uncomfortable.
The reverse can also contribute to a noticeable change in how weather feels. If a period of warm, humid conditions is followed by cooler and drier air, the contrast can make the new weather seem particularly cold.
The Met Office notes that temperature alone does not capture the complete outdoor experience. Wind, humidity and sunshine can all influence how warm or cool conditions feel.
Sunshine can make the same temperature feel different
Sunlight also affects how you experience the weather.
A 20°C afternoon in direct sunshine can feel dramatically warmer than 20°C under cloud, particularly if there is a breeze.
Your surroundings also matter. Dark surfaces such as roads and pavements can absorb solar energy and become warm, while shaded areas can remain noticeably cooler.
This means you may feel comfortable in the sunshine but immediately reach for another layer when walking into the shade.
It is another reason why the temperature shown in a weather app should not necessarily determine what you wear on its own.
Why your wardrobe can change so quickly
There is also a psychological and behavioural element to the transition between seasons.
After weeks of hot weather, people often become accustomed to lightweight clothing, sandals and short sleeves. When conditions change, even slightly, the contrast can feel dramatic.
A temperature of 23°C may have previously encouraged you to leave the house in a T-shirt. After a prolonged period of hotter weather, a cooler breeze and cloudy sky can make the same temperature seem much less inviting.
Your clothing choices then reinforce the sensation. Once you put on a jumper, your body retains more heat, which can make the cooler conditions feel more comfortable.
This does not mean your perception is inaccurate. Rather, temperature perception is influenced by both your surroundings and your body's recent experience.
How long does it take to adjust?
Temperature acclimation does not happen instantly.
Michigan Medicine notes that people can take around 10 to 20 days to adjust to a new seasonal environment, although the exact experience varies between individuals.
This helps explain why the first cooler spell after a hot period can feel unusually dramatic.
After several days or weeks of cooler weather, your body may gradually adjust again. Eventually, a temperature that initially felt cold can become your new normal.
This is also why the first warm days of spring can feel extraordinarily hot even when temperatures are relatively modest.
What should you check before deciding what to wear?
Rather than looking only at the maximum temperature, consider the wider weather conditions.
Check the wind speed, humidity and "feels like" temperature, particularly if you are going to spend a lot of time outdoors.
The Met Office specifically recommends considering the "feels like" temperature because it accounts for factors such as wind and humidity that affect how conditions are experienced by the human body.
You should also consider whether you will be walking, sitting outside, travelling through exposed areas or spending time in direct sunlight.
A light layer can be useful during unpredictable weather because it allows you to respond to changing conditions without committing to a full autumn wardrobe.
The bottom line
Feeling cold at 23°C does not necessarily mean something is wrong with you. After an extended period of hot weather, your body can become acclimatised to higher temperatures. When the weather changes, a moderate temperature can therefore feel surprisingly cool.
Wind, humidity, sunshine and your recent exposure to different temperatures can all influence the experience.
So, if you find yourself shivering while the thermometer insists it is still summer, there is a perfectly reasonable explanation. Your body's internal temperature system is constantly adapting to its environment.
And before you pack away every T-shirt and declare autumn officially here, remember that British weather can change quickly. A chilly spell does not necessarily mean summer has disappeared for good.
Sources
- University of Michigan Medicine, "Why a 65-degree day feels cold in fall but warm in spring.
- Met Office, "What is 'feels like' temperature?
Disclaimer: This article is for general information and educational purposes only. It is not medical advice or a diagnosis. If you experience persistent or unexplained sensitivity to cold, particularly alongside other symptoms, consider speaking with a qualified healthcare professional.