Paris flats were never designed for heat: zinc roofs, top-floor rooms tucked under the eaves, small spaces with little airflow, courtyards where the air never moves. Once a heatwave settles in, indoor temperatures climb fast and come down painfully slowly. The good news: a few well-timed habits — the same ones recommended by France's energy agency ADEME and the health authorities — will keep you several degrees ahead, no air conditioning required.
How do you keep a flat cool without air conditioning?
By working the shutters and windows at the right moments: everything closed during the day as soon as the sun hits, everything open at night as soon as the outside air turns cooler than the inside. It is the habit ADEME puts at the top of its recommendations — timed well, it keeps you several degrees ahead without a single watt of AC.
And the timing is won or lost by a couple of hours. ADEME repeats it every summer: close the shutters before the sun hits the windows — from mid-morning on the east side, then the south and west sides as the day goes on. Keep the windows shut too: as soon as the air outside is hotter than the air inside, airing the flat heats it up.
In the evening, flip everything. When the outdoor temperature finally drops below your indoor one — often late, between 10 pm and midnight at the peak of a heatwave — open wide and let the air flow all night and into the early morning. This night-time ventilation cools the walls, not just the air: it is what makes the next day bearable.
No shutters, like many older Parisian buildings? Thick, light-coloured curtains (or thermal blackout curtains) drawn on the sunny side make a real difference — ADEME recommends light colours, which reflect the sun's radiation instead of absorbing it.
Create a cross-draught
If your flat has windows on two façades (street and courtyard), open both sides at night and wedge the inner doors open: hot air escapes on one side, cooler air comes in on the other. In a single-aspect studio, help the air along with a fan placed at the window, blowing outwards, to push out the day's accumulated heat — then turn it back towards you once the room has been flushed.
Is a fan enough to keep you cool?
Yes — on one condition: pair it with water. A fan alone does not cool the room, it just moves air; but on damp skin, that airflow speeds up evaporation and feels 2 to 3°C cooler, for about €8 of electricity a year according to ADEME (a portable AC unit runs closer to €140).
Hence the Santé.fr recommendation to combine it with: wet your body regularly, at least your face and forearms — a mist spray, a damp cloth, a room-temperature shower. Damp skin plus moving air is the most effective cooling you can get without AC.
As for the famous wet sheet in front of the fan: the principle — evaporative cooling — is real, but the effect is modest: a few degrees at best, mostly when the air is dry, and it adds humidity to the room, which can turn unpleasant on muggy nights. Worth trying; don't expect a miracle.
Buy the fan before the heatwave
Obvious advice, ignored every single year: fans vanish from the shelves within the first 48 hours of a heatwave. ADEME is clear that a home should be prepared before the heat arrives. Buy, dig out, dust off and test your gear in June — not the day Météo-France puts the Paris region on orange alert. Our heat-survival gear guide exists for exactly that.
Floor and orientation: play the hand you have
- Top floor under a zinc roof: the toughest setup — the roof keeps radiating heat late into the night. Sleep in the coolest room, even if that's the living room or the hallway.
- South- or west-facing: close up even earlier — the low, lingering late-afternoon sun is the worst.
- Courtyard-facing, lower floors: often the coolest rooms in the building; that's where the mattress goes.
- Switch off what heats: oven, hob, game console, router, halogen lamps — ADEME recommends limiting every heat-producing appliance during the day.
Why does Paris stay hot at night?
Because of the urban heat island effect: stone and asphalt soak up heat all day and release it after sunset, so central Paris cools down badly at night — a phenomenon at its strongest on heatwave nights. In practice, on some nights the temperature barely drops and night ventilation gives less relief. All the more reason not to let a single extra degree in during the day — and to head for parks and riverbanks in the evening, noticeably more breathable than mineral streets.
When the flat is no longer enough
The health authorities recommend spending the hottest hours somewhere cool: a library, cinema, museum, pool or church. Our map of cool places around you exists for exactly that. And if you still develop an intense headache, dizziness or nausea, don't stay on your own: read our guide Heatwave: what to do for your health — and if severe warning signs appear, call 15 (or 112).