Why do we like to sleep under the covers even when it’s hot?
19-6-2026
Translation: Elicia Payne
We all know the feeling. Your bedroom feels like an oven, your pyjamas are sticking to you and sleep is out of the question. Yet we still choose to be under the covers. It sounds contradictory, but there are good reasons for it.
I just can’t do it – sleep outside the covers. Surely it makes perfect sense to do without them on hot summer nights. My mind says one thing, but my body says another. Why’s that? Because our bodies cool down before we sleep. One to two hours before our usual bedtime, the body’s core temperature starts to sink (link in German) and we get tired. You may have heard of the circadian rhythm, or our «inner clock».
The cooling happens regardless of what cover we use or the room temperature. In higher temperatures, we feel more alert; when it cools down, we get tired. And yet we still need the covers or blanket. Without one, our body would get too cold during sleep and we’d wake up. During REM sleep, the body is less able to regulate its temperature. The covers help prevent this natural temperature drop, creating a warmer «microclimate» right next to the skin.
Maybe you’ve also found that a hot shower in the evening helps. The body then cools down very quickly, and the sleep signal is amplified.
A 200,000-year-old habit
The need for a protective layer while sleeping is probably as old as humanity itself. Archaeological discoveries from South Africa show that humans were already making sleeping mats at least 200,000 years ago. They were made of grass and leaves from plants that keep insects away. These weren’t just simple places to lie down, but small sheltered retreats. So today’s covers are the product of a very old idea.
On top of that, there are cultural influences such as being wrapped up as children. For one thing, babies aren’t very good at regulating their body temperature – they cool down even faster than adults. For another, being wrapped up is an act of affection and care before falling asleep. You could call it conditioning, that is, a habit that runs deeper than any reason. We associate falling asleep with covers.
Weight is comforting
Another reason for wanting to be under the covers is due to a psychological factor. The weight of a duvet or blanket can have a calming effect because it exerts a gentle pressure on the body. This effect – known as deep (touch) pressure stimulation – can reduce stress and have a calming effect by activating the parasympathetic nervous system. Our need for comfort can override the feeling of being too warm.
Mixed signals
If it’s hot in the bedroom and you try to fall asleep without a cover, you’re confusing your body. On the one hand, you’re helping it by not trapping heat under the covers. On the other hand, your mind is calling for the covers – because a cover means it’s time to go to sleep. And you feel safer knowing you won’t be cold in the night.
That’s why hot summer nights are often less restful. You have to overcome your instincts and fall asleep without a cover. And there’s a good chancec you’ll wake up at some point during the night and pull the covers over your freezing body after all.
Are we victims of evolution?
Perhaps, over thousands of years, we humans can unlearn what our great-great-great-grandparents taught us – that we need a blanket for sleeping. In the animal kingdom, sleeping under a cover is far from universal. There are even groups of people who regularly sleep without any covers. That said, the study in question from 2002 only examined very small groups in South Africa, the Congo, and Namibia. These communities of hunters, gatherers and farmers had the advantage of living in climates where it didn’t usually get particularly cold at night. They also kept warm by sitting around a fire or huddling close together.
Those of us in Central Europe, on the other hand, have spent millennia in regions with cold nights, where covers weren’t optional but a matter of survival. On top of that, most of us now sleep alone, with little to no physical contact. Without a crackling fire and no group huddling, the blanket has essentially become a substitute for warmth and security.
So the fact that we sleep under blankets isn’t just a force of habit with evolutionary roots – it’s a tangible physical necessity, since we can’t regulate our body temperature while we sleep. We have a genetic predisposition to getting cold. And in our culture, covering up has become the norm, even when it’s no longer biologically necessary – like on hot nights.
Martin Jungfer
Head of Content
Martin.Jungfer@digitecgalaxus.chJournalist since 1997. Stopovers in Franconia (or the Franken region), Lake Constance, Obwalden, Nidwalden and Zurich. Father since 2014. Expert in editorial organisation and motivation. Focus on sustainability, home office tools, beautiful things for the home, creative toys and sports equipment.
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