Ventilate
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When to air your home in autumn and rain

Autumn rain and cool air change when to open. Close before the shower, keep the blinds open for daylight, then air wide for a few minutes in a dry spell.

In a heatwave the question is simple: is the air outside cooler than the air inside? In autumn the answer is almost always yes, and that stops being the useful question. The air is cool, the sky is grey, showers come and go, and the heating is starting to run.

You still need fresh air. Cooking, showers, drying laundry, and just breathing load a closed home with moisture and stale air. The goal changes: swap the air without losing the warmth, and without letting the rain in.

The autumn checklist

  • Close before the shower arrives. A wet sill and damp curtains are not airing
  • By day, keep the window shut and the blinds open. Daylight through glass is free light and a little free warmth
  • Air in the dry spells between showers: open wide for a few minutes, then close
  • Open fully rather than leaving a window tilted all day. A short wide opening swaps the air. A tilted sash cools the walls around it for hours
  • Turn the radiator down while you air, and back up once the window is shut
  • At night, once it is cold outside, keep the windows closed

Close before the shower

Rain is the clearest signal of the season. Water on the sill and frame, wet curtains, and a damp floor under the window add moisture to a home that already has too much. A shower driven by wind can also soak a room faster than you expect.

Ventilate reads the hourly forecast. When rain is expected, the advice is to close. By day it keeps the blinds open so the room still gets light, and a rain warning appears on the dashboard so you know why the plan changed. When the shower has passed, the advice moves on with the weather.

Window shut, blinds open

In summer you close shutters and blinds against the sun, because sun through glass is the biggest heat source in the room. In autumn and winter that same sun is on your side.

On a cool or rainy day, Ventilate can suggest a fifth state that does not exist in a heatwave: close the window, keep the blinds open. You keep the warmth you already have, and you let the daylight in. A south-facing room on a clear autumn afternoon can warm up noticeably before the heating does anything.

At night that light is gone. Close the window. If you have shutters or heavy curtains, closing them too keeps a little more warmth in the room.

Air in the dry spells

Brief, wide airing is the standard advice for every season. The French ministry for ecology recommends opening windows wide in every room for at least 10 minutes a day, summer and winter, and while cooking or cleaning.

Autumn just makes the timing matter more:

  • Wait for a dry gap. After a shower passes, the air is often clean and the rain has stopped hitting the glass
  • Pick the mildest hours. Late morning or early afternoon is usually warmer than the evening
  • Open wide, then close. Two windows on opposite sides swap the air in minutes. A single window takes a little longer
  • Do it more than once. Two or three short openings beat one window left cracked all afternoon

Short openings change the air without chilling the walls, floors, and furniture. Those surfaces hold most of the warmth in a room, so the air warms back up quickly once the window is shut.

Ventilate does not run an airing timer, and it does not measure CO₂ or indoor humidity. It tells you when rain or cold outdoor air means the window should stay closed, so you can choose your few minutes around it.

Mild autumn evenings still count

Not every October day is cold. After a warm spell, a flat can still sit above 20 °C while the evening air outside is a few degrees cooler. On those evenings the summer rule still works: compare indoor and outdoor temperature and open while the outside is cooler.

Once outdoor air drops below about 15 °C, Ventilate stops suggesting a long opening and switches to keeping the heat in. That is the moment to move from a night flush to short airing.

Where to go next

The World Health Organization treats 18 °C as a sensible minimum indoor temperature in the cold season. If short airing keeps pulling your rooms below that, air less often and for less time.

This is not medical advice. If cold or damp is making you unwell, follow your local health agency.

Updated

Sources and further reading

Official guidance supporting the practical advice on this page.

Links checked 29 August 2026.

More in this guide

When it is warm and dry: how to ventilate

Hot, dry weather is the easiest heat to work with. Close and shade by day, then open wide when outdoor air is cooler, often after sunset. Dew point stays low.

When it is warm and humid: how to ventilate

Muggy heat is harder. High dew point means air will not cool your skin well. Prefer a short opening when outdoor air is only a little cooler. Keep sun off the glass.

When it is cold: brief airing, keep the heat

In true cold, keep the heat you already paid for and air in short bursts. Then close. Take winter sun through closed glass. Skip long night airing when it is very cold.

When it is cold and humid: short damp airing

Damp cold is common on Atlantic coasts. Rooms can feel clammy without being icy. Air briefly when it is not raining, then close. This is not a mold diagnosis.

Mediterranean climate: shutters and night flush

Hot, dry summers and milder, wetter winters. Shutters down by day. Night flush when the street cools. In winter air briefly and take light through closed glass.

Continental climate: hot summers, cold winters

Continental summers run hot and winters run cold. Shade and flush at night in summer. After a heatwave keep night ventilation. In winter air briefly, then close.

How weather changes when you ventilate · All guides

These guides are informational and are not medical advice. If heat is making you unwell, follow your local health agency’s guidance.