What do people get wrong about the rainy season in Japan?

This answer is a draft. It stays unpublished until legal review and source verification are complete.

Early summer brings several weeks of high humidity. Households here treat it as a season with its own tasks — and one of those tasks has a five-hour deadline.

Two things the season does

1. It slows drying. Laundry that stays damp beyond about five hours lets Moraxella bacteria multiply — the source of the "indoor-dried" smell identified in Kao's 2011 research. Fans, dehumidifiers and bathroom dryers exist to beat that clock. 2. It grows rice. The season is part of how the crop is watered and how reservoirs are refilled. Inconvenient and necessary at the same time.

[Verify] Confirm the Moraxella finding with Kao's published material, and seasonal timing with the Japan Meteorological Agency.

Misunderstanding 1｜It rains constantly

It does not. The constant is the humidity, not the rain.

Misunderstanding 2｜It is the same everywhere in Japan

Timing and intensity differ by region, and Hokkaido is generally not counted as having one. Check the region you are in.

Misunderstanding 3｜Closing the windows keeps damp out

Sealed rooms trap the moisture already inside. Ventilation in the drier hours, or a dehumidifier, is the usual approach.

Misunderstanding 4｜It only affects laundry

Cupboards, shoes, tatami and stored clothing all matter. This is why airing things out is a seasonal habit.

Misunderstanding 5｜It is purely a nuisance

See point 2 above. Rice does not grow without it.

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Sources

• Japan Meteorological Agency — rainy season onset and end dates

https://www.data.jma.go.jp/cpd/baiu/

• Kao Corporation — research on the cause of indoor-drying odour (2011)

https://www.kao.com/jp/

• Ministry of Agriculture, Forestry and Fisheries — rice cultivation

https://www.maff.go.jp/j/seisan/kikaku/

⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.

About this article

What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.

This is general information. Results vary from person to person and depend on your own conditions and surroundings.

Please decide for yourself, using your own judgement, whether any of this suits your situation. We cannot accept responsibility for any damage, loss or injury arising from following this article.

Always follow the instructions on any appliance or product you use, and never mix cleaning products.

Sources

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