What do people get wrong about Japanese summer heat habits?
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Japanese summers combine 35°C days with 70–80% humidity, and the country records tens of thousands of heatstroke ambulance calls a year. The everyday responses — from the salt sweets in every office to the wet towels around the neck — look like folklore. Most map directly onto public-health guidance.
The scale of the problem
| Item | Figure | Source |
|---|---|---|
| Heatstroke ambulance transports, May–September 2024 | 97,578 (second-highest on record) | Fire and Disaster Management Agency |
| Share occurring at home | about 40% | same |
| Share aged 65 and over | about 58% | same |
| Heat-Stroke Alert threshold (WBGT) | 33°C; "Special Alert" at 35°C (since 2024) | Ministry of the Environment |
[Verify] Transport figures with the FDMA's annual heatstroke report (the 2023 figure was 91,467); WBGT thresholds with the Ministry of the Environment's heat illness prevention site.
Habits and what they do
| Habit | Mechanism |
|---|---|
| Uchimizu (sprinkling water on pavements at dusk) | Evaporative cooling of the surface; works when the sun is off the ground, not at noon |
| Sudare / yoshizu (reed blinds outside the window) | Blocks solar gain before it reaches the glass — more effective than curtains inside |
| Neck towel, cooling towel | Cools blood near the surface; wet and re-wet |
| Salt sweets, barley tea | Replaces sodium and fluid lost in sweat — barley tea is caffeine-free and the standard summer drink |
| Hand fan (sensu/uchiwa) | Moves air over sweating skin; no battery |
| Yukata, linen, loose cuts | Airflow and evaporation |
Misunderstanding 1｜Air conditioning is unhealthy; endure it
About 40% of heatstroke transports are from homes, and older people are the majority. The Ministry of the Environment says to use air conditioning without hesitation, aiming for a room around 28°C, and to check on elderly relatives who "do not feel hot".
Misunderstanding 2｜Drink only when thirsty
Thirst lags need, especially in older people. Guidance: drink regularly, about 1.2 L a day beyond meals in ordinary conditions, and add salt (0.1–0.2%) when sweating heavily.
Misunderstanding 3｜Uchimizu at midday cools the street
At midday the water evaporates instantly and the humidity rises. Households sprinkle in the early morning and at dusk, on shaded ground.
Misunderstanding 4｜Curtains block the heat
Once sunlight is through the glass, much of the heat is inside. Exterior shading — sudare, awnings, a green curtain of climbing plants — is why old houses were survivable.
Misunderstanding 5｜Children in strollers are in the shade
A stroller seat sits close to the hot pavement, often several degrees hotter than at adult head height, and the canopy traps heat. Use a sunshade with airflow, a wet towel, and check the child's back.
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Sources
- Ministry of the Environment — Heat illness prevention information site (WBGT, alerts)
https://www.wbgt.env.go.jp/en/
- Fire and Disaster Management Agency — Heatstroke ambulance transport statistics
https://www.fdma.go.jp/disaster/heatstroke/post3.html
- Ministry of the Environment — Cool Biz and summer guidance
https://ondankataisaku.env.go.jp/coolchoice/coolbiz/
⚠️ 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.
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