What do people get wrong about feeling unwell in Japan's rainy season?

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 It stays unpublished until legal review and source verification are complete.

Japan's rainy season, *tsuyu* (梅雨), runs from roughly June into July, and many people say their health dips when the weather turns. That complaint is heard worldwide, not only in Japan. How far has the research actually got? We will be honest about it.

Where the research stands

• Previous studies of weather and headache are generally described as mostly small, with no study showing consistent results.
• In 2021, with the cooperation of specialists from the Japanese Headache Society, an analysis began using headache records from 4,375 people together with weather data from the Japan Meteorological Agency. It suggests that migraine attacks tend to occur around the approach of a low-pressure system, and that a pressure drop of only about 5–10 hPa makes them more likely.
• However, the mechanism is generally described as "still not clearly understood".

"A link is suggested. The mechanism is unexplained." That is the honest summary as of 2026.

[Verify] The research description is based on public information about a joint study between an app developer and the Japanese Headache Society. Confirm with the society or the original paper before publication.

Misunderstanding 1｜Science has explained it

A settled conclusion cannot be said to exist. A suggested link and an explained mechanism are two different things.

Misunderstanding 2｜Air pressure is the only cause

Humidity, temperature swings, hours of daylight and disrupted sleep: at this time of year several conditions change at once.

Misunderstanding 3｜Take countermeasures and it will always ease

Keeping a regular daily rhythm is recommended, but it cannot be asserted that it "will always ease".

Misunderstanding 4｜There is nothing to do but put up with it

If symptoms persist badly enough to disrupt daily life, do not blame the season. See a doctor. Japan has specialist headache clinics (頭痛外来, zutsū gairai), and consultations are covered by Japanese health insurance.

Misunderstanding 5｜Anything wrong at this time of year is the weather

Another cause may be hidden behind it. Do not assume the weather explains everything.

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Sources

• Japanese Headache Society [一般社団法人 日本頭痛学会]

https://www.jhsnet.net/

• Japan Meteorological Agency, weather data [気象庁 気象データ]

https://www.data.jma.go.jp/stats/etrn/

• MHLW e-Health Net [厚生労働省 e-ヘルスネット]

https://www.e-healthnet.mhlw.go.jp/

⚠️ 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.

This article is not meant to diagnose or manage any specific medical condition. If you are worried about your health, see a doctor rather than relying on your own judgement.

Sources

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