You suddenly feel colder than it actually is

Yesterday, while walking from the station to the office, I concluded that summer must be officially over. From outfits alone, one had to surmise that back-to-school autumn energy had swept in a week and a half early.

I saw people clad in roll-neck jumpers and sweaters, wool trousers and coats — coats! — not jackets. For the first time in about four months, there wasn’t a single foot on show; they were tucked away in socks and closed-toe shoes, their time in sandals already a distant memory.

I myself was no different. Having woken up and started shivering as soon as I slipped out of bed (a welcome sensation after so many mornings starting the day already clammy), I’d dressed accordingly: sturdy trousers, a top and jumper, socks and hefty lace-up boots to tramp through the rain-splattered streets.

I would have guestimated the temperature to be somewhere between 10 and 15 degrees; not quite single digits, but not far off. The thermometer, however, told a very different story. It was 23˚C. But that’s... hot? I thought, utterly bewildered. In fact, it’s what I’d usually describe as my perfect summer temperature, the ideal slug of warmth without straying into sweltering territory.

So why do we all feel so chilly and in need of wrapping up when what we’re experiencing would normally be considered a balmy day? There is actually science behind our internal thermostats seeming collectively broken — the same phenomenon that explains why you’ll see Spaniards and Italians in puffer jackets when you’re sweating in swimwear on holiday. Thermoception is our bodies’ perception of temperature; to perceive temperature, we have specialised sensory receptors called thermoreceptors. But far from being something that’s just detected by our skin, whether we feel hot or cold is really determined by our brains, the nerve centre that regulates our core temperature by activating sweat glands and controlling blood flow and heart rate in response to environmental changes.

“Warm” and “cool” are subjective feelings (unlike temperature, which is an objective measurement). After a period of hot weather, like we’ve been experiencing in the UK, we get used to warmer temperatures – a sudden drop, therefore, feels cooler. “When you’re exposed to a lot of heat outside, basically there’s an adaptation going on — your body will get used to it and lower the threshold at which you start to cool off,” says Laure Rittié, a research assistant professor of dermatology at the University of Michigan. “There are a lot of physiological processes that take place.”

The main process is called acclimation or acclimatisation, defined as the short-term adjustments we make to changes in our environment. As part of that process, the parameters or baseline at which your body might deploy the various mechanisms required for thermoregulation — automatic reflexes such as shivering or sweating and conscious behaviours like changing clothes — can change depending on what feels “normal”.

Our bodies get accustomed to feeling a certain way and adapt and respond accordingly (your mum’s admonition to take your coat off “or you won’t feel the benefit” when you were a kid was actually bang on the money). For example, physiological adaptations that occur during repeated exposure to a hot environment include reduced body temperature, reduced heart rate and increased sweating efficiency, according to a heat acclimation study conducted by the University of Connecticut.

Then there’s the fact that the actual temperature and what it feels like can be very different depending on other weather factors. This is because “our bodies respond not just to temperature, but also to wind, humidity and sunshine,” says the Met Office. “Together, these factors help explain why a spring day can feel chilly despite clear skies, or why a summer afternoon can feel uncomfortable even at relatively modest temperatures.”

Wind chill is particularly significant; moving air removes heat from the body quicker than still air, so a calm day might feel several degrees warmer than a blustery one. Then there’s humidity, the other key component that can have a noticeable impact on temperature versus “feels like”. This describes the moisture in the air — the higher the humidity, the slower sweat evaporates from the skin, making it harder for our bodies to cool down and regulate. On the flip-side, drier days feel cooler.

After weeks of hot temperatures with frequent high humidity, it’s little wonder that a noticeable drop in degrees and drier, breezier weather might send us scuttling back to our winter wardrobes. Just don’t get too comfortable back in knits — the Met Office is predicting a potential September heatwave heading our way...