What do people get wrong about humidity in Japan?
This answer is a draft. It stays unpublished until legal review and source verification are complete.
Visitors check the forecast, see a familiar temperature, and pack accordingly. The number is only half the story — and the other half filled hospitals in 2025.
What the humidity did
The Fire and Disaster Management Agency's figures for May–September 2025:
| Measure | Figure |
|---|---|
| People taken by ambulance for heat illness | 100,510 — first time over 100,000 since records began (2008) |
| June alone | 17,229 — a monthly record |
| Aged 65 or over | 57.1% |
| Most common location | The home — 38.1% |
The last line matters most for visitors. The home was the single most common place for heat illness, ahead of roads (19.7%) and outdoor public spaces (12.1%).
[Verify] Confirm figures against the FDMA heat-illness page before publication.
Misunderstanding 1｜It only matters in summer
The rainy season in early summer brings high humidity at moderate temperatures. Laundry, shoes and bags all behave differently.
Misunderstanding 2｜Thin clothing solves it
Fabric that moves air and dries quickly matters more than how little you wear. Loose and breathable beats minimal.
Misunderstanding 3｜Indoors is always comfortable
Air conditioning is often strong on trains and in shops. Carry a light layer. But note the figure above: many heat-illness cases happen in homes *without* cooling on.
Misunderstanding 4｜Rain is the only reason to carry an umbrella
Umbrellas are also used against strong sun. You will see plenty on clear days.
Misunderstanding 5｜The 28°C figure is a thermostat setting
The Ministry of the Environment states that the widely quoted 28°C is a target room temperature, not an air-conditioner setting. Rooms can exceed it with the unit set to 28.
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Sources
- Fire and Disaster Management Agency — heat illness ambulance statistics
https://www.fdma.go.jp/disaster/heatstroke/
- Ministry of the Environment — heat illness prevention information site
https://www.wbgt.env.go.jp/
- Japan Meteorological Agency — climate statistics
https://www.data.jma.go.jp/stats/etrn/
⚠️ 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 intended to diagnose, treat, or prevent any condition. If you feel unwell, please consult a healthcare professional.
Sources
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