In Morocco, Algeria, Spain or Greece, residents have known it for generations: summer is not a season for sleeping like in winter. Meridian nap, shutters closed at dawn, linen bedding, bodies accustomed to the heat and short nights. In these cultures, the relationship with summer sleep is intuitive, transmitted from mother to daughter, adjusted to the sun. In France, where heatwaves have become an annual reality since the tragedy of 2003, we are still learning.
Why heat sabotages your sleep
The human body falls asleep when its internal temperature drops. It is a fundamental physiological mechanism: the temperature drop of approximately one degree triggers the secretion of melatonin and prepares the brain for rest. When the room is 28 or 30 degrees, this cooling does not occur. The body struggles, sweats, agitates. We end up dozing off exhausted, but sleep remains light, fragmented, not very restorative. Result when waking up: fatigue which adds to fatigue.
L’National Institute of Sleep and Vigilance recommends a bedroom temperature between 16 and 20 degrees for optimal sleep. In a heatwave, reaching even 24 degrees is a challenge. This is where specialist strategies come into play.
What people in hot countries do
The Greeks close their shutters at 7 a.m. and only reopen them at sunset, thus maintaining natural thermal inertia in stone houses. Moroccans sleep on woven mats which allow air to circulate under the body, preventing overheating by contact. The Spanish institutionalized the nap not out of laziness but out of physiological intelligence: sleeping for around twenty minutes at the start of the afternoon, at the peak of the heat, allows you to recover without disrupting the evening circadian cycle.
These habits all have one thing in common: they work with heat, not against it. We are not trying to reproduce the conditions of a cool night. We adapt the body and the environment to the reality of the season.
The six-point protocol
Dr. Damien Léger, head of the Sleep Center at the Hôtel-Dieu in Paris, and the recommendations of Public health France converge towards the same essential gestures.
Occlude early. Close shutters and curtains before the sun hits the facades, ideally from 8 a.m. Stone and concrete store heat: it is better never to let it in.
Ventilate at night only. Open the windows when the outside temperature drops below the inside temperature, often after 10 or 11 p.m. Create a transverse air current.
Refresh the body, not the room. A mist on the face, a damp towel on the wrists, and a lukewarm (not cold) shower before bedtime help the body begin its thermal descent.
Lighten the bedding. Linen or cotton percale, a single thin sheet, honeycomb latex pillow that does not retain heat. Memory foam mattress toppers should absolutely be avoided in heatwaves.
Review schedules. Going to bed later when the nights are warm is physiologically justified. Forcing sleep at 10 p.m. in a 29-degree room is counterproductive. Better to read until midnight and sleep in one piece.
Adopt the micro-nap. Twenty minutes maximum between 1 and 3 p.m. No more, otherwise it will disrupt your nighttime sleep. It is the best kept secret of the Mediterranean countries, and one of the best validated by research in chronobiology.
The heatwave will not last. But the nights of July and August become tamer. Sometimes you just have to look at how those who have always known them live.
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