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Too hot to sleep? Our ideas on how to get some sleep in the middle of a heat wave.

Some nights, we think that air conditioning is a good idea. Especially when it's past 9pm and still over 30°C. But rather than rush to equip ourselves - and heat up the outside air even more - we tested a few easy-to-follow ideas. And we know: it is possible to sleep in the middle of a heat wave without an air conditioner.

Circulate fresh air

The quest starts early, very early. Just after sunrise, when the sun's rays are not yet sufficient to warm the earth, the air temperature is the lowest of the day. This is the best time to open the windows wide and cool down your home. And at the end of the morning, or as soon as the sun approaches the facade, we close the shutters, the curtains and even the windows to avoid the entry of hot air.

If you got up too late, there is still the draught option. Nothing could be easier when you live in a house. In this case, the windows closest to the ground allow the coolest air to enter. In an apartment, it is less obvious but still feasible. The stairwell, which is often not very exposed to the sun, stays cooler for longer than the apartments. If there are windows, open them to let the air circulate. And if you spend the day at home, you can even open the door for a few moments to take advantage of this.

Switching your bed to daylight saving time

Adapting your bed to the season is ideal for maximizing your chances of finding sleep. There's no need to move it to the coldest room (which can make it very hot). It's the bed linen that really counts.

Synthetic materials, such as polyester, retain moisture and heat. It is difficult for the body to cool down in these conditions. Natural, absorbent and breathable materials are preferred. Sheets made of cotton percale, fine and cool to the touch, are very pleasant in summer. But in hot weather, our favourite fabric is linen. Its fibres have a thermoregulatory action: they absorb and evacuate heat and perspiration, which helps the body to maintain the right temperature. You can wear it during the day or sleep in it at night.

You can also literally cool your bed. Half an hour before going to sleep, you can put a hot water bottle filled with very cold water, ice packs, cold packs... Anything that will bring a little freshness, even if it's only for the time it takes to fall asleep. It seems that you can even give your sheets a little stay in the freezer before making your bed again. We haven't tried it, but the idea is tempting.

Refresh before bedtime

To fall asleep, our internal temperature must decrease by about 1°C. This biological process is a challenge at the height of summer, especially since the hottest part of the day is in the late afternoon, between 4 and 6 pm. A good excuse to cancel the sports class scheduled for this evening. Or postpone it to the next day and let off steam in the cooler hours of the day.

To get a good night's sleep, it's essential to stay well hydrated throughout the day. Doctors say it, newspapers say it, news channels say it, your parents say it, but we can't say it enough. Drinking (water) allows the body to sweat to regulate its internal temperature and to compensate for dehydration, which is more frequent when nights are too short. In fact, a study conducted in the United States and China(1) has shown that nights of less than 6 hours increase the risk of dehydration by 16 to 59% in adults. So make sure you drink enough water at room temperature, which is more quickly absorbed by the body.

For dinner, there is only one watchword: freshness. Avoid turning on a heat source (oven, hotplates, etc.) so as not to heat up the room. And just before going to bed, a lukewarm shower allows you to refresh yourself without getting cold, and without encouraging your body to warm up right afterwards. You can keep a mister handy during the night to reproduce the same effect. And if you share a bed, it may be best to sleep in separate rooms just for the night.

What if you still can't sleep?

When our lifestyle allows it, we don't hesitate to shift our sleep rhythm by a few hours. Going to bed later and sleeping a little longer, when the air is more breathable, is ideal. Taking a short nap in the afternoon also helps you recover after a short night. And when insomnia persists, why not take advantage of the slight drop in temperature at night to get some fresh air? In Paris, 13 parks and gardens are open 24 hours a day in summer, and there are even more during the heat wave. And some museums are too. A nice way to ride the heat wave.

(1)Short sleep duration is associated with inadequate hydration: cross-cultural evidence from US and Chinese adults, Asher Y Rosinger, Anne-Marie Chang, Orfeu M Buxton, Junjuan Li, Shouling Wu,Xiang Gao, Sleep, Volume 42, Issue 2, February 2019.