Coping with Japan's summer heat: heatstroke alerts, timing and what to buy
Checked against 17 official sources. 7 minute read.
What to know first
From late June to mid-September, much of Japan is hot and humid enough to cause heatstroke in healthy adults. Plan outdoor sightseeing for before 10:00 and after 16:00, spend the middle of the day indoors, and drink before you're thirsty. Check the heat index (WBGT, 暑さ指数) each evening: a Heat Stroke Alert (熱中症警戒アラート) means a WBGT of 33 or more is forecast somewhere in the forecast area (usually the whole prefecture), and a Special Heat Stroke Alert (熱中症特別警戒アラート) means 35 or more is forecast at every monitoring point in the prefecture. On an alert day, cut outdoor time hard. If someone becomes confused, can't drink or collapses, call 119.
Next step: Bookmark the Ministry of the Environment's English heat page and check it at 17:00 the day before each outdoor day.
- 2026 alert season
- 22 April to 21 October 2026
- Heat Stroke Alert threshold and timing
- WBGT 33 at any point in the forecast area; 17:00 day before and 05:00 on the day
- Special Heat Stroke Alert
- WBGT 35 at all points; 14:00 day before
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On this page
What to do: situation by situation
| Your situation | What to do |
|---|---|
| WBGT under 25 | Normal sightseeing; drink regularly. |
| WBGT 25–28 (警戒, warning) | Take a shaded break every hour; avoid strenuous walks at midday. |
| WBGT 28–31 (厳重警戒, severe warning) | Avoid direct sun; plan indoor time from 11:00 to 15:00. |
| WBGT 31 or above (危険, danger) | Avoid going out where you can and move to a cool room; if you must be outside, keep it short and early. |
| Heat Stroke Alert issued | Move outdoor sights to before 09:00 or after 17:00; book indoor alternatives. |
| Special Heat Stroke Alert issued | Treat it as a stay-indoors day except for short essential trips. |
| Travelling with children or people over 65 | The ministries ask for extra care; as our own cautious rule of thumb (not an official rule), plan as if the WBGT were one band higher. |
| Someone feels dizzy, has cramps or a headache | Move to a cool place, cool them, give fluids with salt. |
| Someone is confused, can't drink, or loses consciousness | Call 119 immediately. |
| Unsure whether to call an ambulance | Call #7119 (42 areas, including all of Tokyo, Osaka and Kyoto prefectures; hours vary by area; mainly Japanese). |
The WBGT bands are those used in Japan's daily-life heatstroke guidelines; the danger band (31+) warns that heatstroke can occur during any activity, even at rest for older people.
How hot it gets
The Japan Meteorological Agency (JMA) reported that summer 2025 (June to August) was the hottest since records began in 1898, with Japan's average temperature 2.36°C above the reference value. The Fire and Disaster Management Agency's confirmed figure is 100,510 people taken to hospital by ambulance for heatstroke between May and September 2025, the most since its survey began in 2008. Humidity is the problem as much as temperature: 33°C in Tokyo feels far harsher than 33°C in southern Europe because sweat doesn't evaporate.
Heatstroke alerts: how they work
Season: in 2026, alerts run from 22 April to 21 October. The 2027 dates had not been announced as of 11 October 2026 (not stated officially); expect a similar spring-to-autumn window and check before you travel.
Heat Stroke Alert: issued at 17:00 the day before and at 05:00 on the day, when the forecast WBGT reaches 33 at any monitoring point in the forecast area, which is usually the whole prefecture (Tokyo has 11 points).
Special Heat Stroke Alert: issued at 14:00 the day before, when the forecast WBGT reaches 35 at every monitoring point in the prefecture, apart from points excluded by regulation. It signals a risk of serious health harm across the whole area.
Where to see them in English: the Ministry of the Environment's heat illness site has an English page showing alert status and WBGT for major cities. The Japan Tourism Agency's free Safety tips app can send push notifications with heatstroke information, alongside earthquake, tsunami and weather warnings.
On TV and phones: alerts appear on NHK weather reports and in Japanese weather apps as 熱中症警戒アラート.
WBGT isn't air temperature. It combines temperature, humidity and sunshine, so a 31°C humid, sunny day can score higher than a dry 35°C one.
Worked example: a Kyoto day under an alert
You're in Kyoto on Tuesday 3 August 2027. At 17:00 on Monday, a Heat Stroke Alert is issued for Kyoto Prefecture with a forecast WBGT of 33.
06:30–08:30 — Fushimi Inari Taisha (the shrine publishes no opening hours or admission charge for the grounds). Coolest part of the day; walk the lower gates only and skip the climb.
08:30–10:00 — Breakfast and rest in the hotel or a café. Shower, change shirt, refill bottles.
10:00–15:30 — Indoor: a museum, a department-store food hall; Nishiki Market is covered but not air-conditioned, so keep it short. WBGT peaks around midday to mid-afternoon.
15:30–17:00 — Rest. Hotel room with air conditioning.
17:00–20:00 — Gion and Pontochō in the evening. Shade from buildings, lower sun.
Shopping list for the day (two adults):
Water, 550 ml (7-Eleven own brand, ¥108 each): 6. Approx. cost: ¥648.
Oral rehydration solution, 500 ml (経口補水液, OS-1, about ¥214 each at a drugstore): 2. Approx. cost: ¥428.
Salt tablets (塩タブレット), 81 g pack: 1 pack. Approx. cost: ¥259.
Cooling body wipes (Bioré cooling sheets, 20 sheets): 1. Approx. cost: ¥380.
Total. Approx. cost: ¥1,715.
Prices checked on 11 October 2026 on the 7-Eleven, Create SD and Yodobashi websites; shop prices vary, and branded drinks or vending machines cost more.
Two adults outdoors for about five hours on a hot day will drink 3 litres or more between them. Refill from hotel water and buy the rest at konbini as you go; for what's on the shelves and the prices, see eating well from convenience stores.
What to buy and where
Barley tea: 麦茶 (mugicha). Where: Konbini, vending machines. Use: Caffeine-free; good for steady drinking.
Sports drink: スポーツドリンク. Where: Konbini, vending machines. Use: Sugar and some salt.
Oral rehydration solution: 経口補水液 (keikō hosuieki). Where: Konbini, drugstores. Use: For mild dehydration, not everyday drinking.
Salt sweets or tablets: 塩飴 / 塩タブレット. Where: Konbini, drugstores. Use: With water on long sweaty walks.
Cooling sheets: 冷却シート. Where: Drugstores, konbini. Use: Forehead and neck; comfort, not treatment.
Neck cooler: ネッククーラー. Where: Drugstores, variety shops. Use: Reusable gel ring.
Parasol: 日傘 (higasa). Where: Drugstores, department stores. Use: Widely used by men and women in Japan.
Cooling wipes and spray: 冷感シート / 冷感スプレー. Where: Drugstores. Use: Quick relief on the move.
For medicine for headaches or stomach upsets caused by heat, see buying medicine in Japan.
Indoor breaks and cooling shelters
Department stores and station buildings are reliably air-conditioned and have seating, toilets and water.
Cooling shelters (クーリングシェルター): since April 2024, cities can designate air-conditioned public and private buildings as cooling shelters (指定暑熱避難施設), which must open to the public, at hours set in advance, when a Special Heat Stroke Alert is issued; some also welcome visitors on other hot days. Kyoto City publishes its lists of city facilities, private buildings and post offices that serve as shelters at https://www.city.kyoto.lg.jp/kankyo/page/0000325269.html (updated September 2026). For other cities, search the city name with クーリングシェルター.
Your hotel room: check the air conditioning works on arrival; see hotel room air conditioning terms.
Okinawa: heat and sudden rain shape the whole day there; see an Okinawa itinerary for rain and hot weather.
Recognising heatstroke and what to do
Early signs: dizziness, heavy sweating, muscle cramps, headache, nausea, unusual tiredness.
What to do:
1. Move into air conditioning or shade.
2. Loosen clothing and cool the neck, armpits and groin with cold bottles or wet cloths.
3. If they're fully alert, give water with salt, a sports drink or oral rehydration solution.
4. If symptoms don't improve, go to a medical facility promptly.
Call 119 if the person is confused, can't drink by themselves, has a seizure, stops sweating while very hot, or loses consciousness. In Tokyo, Osaka and Kyoto, #7119 gives medical advice by phone when you're not sure, mainly in Japanese. The JNTO Japan Visitor Hotline (050-3816-2787, 24 hours, English) gives help in English in an emergency such as an accident or illness. See emergency numbers and visitor help for how these services work, and what travel insurance should cover for hospital bills.
Your next step
Bookmark the Ministry of the Environment's English heat page (wbgt.env.go.jp/en) and set a daily 17:00 reminder to check tomorrow's alert for where you'll be.
Key facts, checked 11 October 2026
2026 alert season: 22 April to 21 October 2026.
Heat Stroke Alert threshold and timing: WBGT 33 at any point in the forecast area; 17:00 day before and 05:00 on the day.
Special Heat Stroke Alert: WBGT 35 at all points; 14:00 day before.
WBGT daily-life bands: 31+ danger; 28–31 severe warning; 25–28 warning; under 25 caution.
Summer 2025 temperature: +2.36°C above the reference value, hottest summer since 1898 (JMA).
Heatstroke ambulance cases, May–September 2025: 100,510 (confirmed), most since 2008 (FDMA, 29 October 2025).
2027 alert season: Not announced.
Cooling shelters: Must open to the public during a Special Heat Stroke Alert.
#7119 coverage: 42 areas, including all of Tokyo, Osaka and Kyoto prefectures.
Kyoto #7119: 24 hours; 0570-00-7119 from IP phones.
Sources for this section: Suginami City, 2026 heat alert operation · Kyoto Prefecture, WBGT and daily-life guidelines · Japan Meteorological Agency, summer (June–August) 2025 climate summary · Fire and Disaster Management Agency, heatstroke ambulance cases May–September 2025 (confirmed) · Kyoto Prefecture, cooling shelters and 2026 alert period · Kyoto City, cooling shelters and lists · Fire and Disaster Management Agency, #7119 implementation areas · Kyoto Prefecture, Kyoto Emergency Advice Center (#7119)
Questions about this guide
How much should I drink?
Japan's "Drink water for health" campaign (backed by the health ministry and now hosted by the Ministry of the Environment) shows an adult man at rest taking in about 2.5 litres of water a day, 1.2 litres of it from drinks. Walking all day in summer you'll need much more: drink small amounts often, before you feel thirsty, and take some salt as well if you're sweating heavily. Don't drink a lot of oral rehydration solution at once, and if a doctor has told you how much to drink because of a kidney or heart condition, follow that advice.
Should I cancel plans on a Heat Stroke Alert day?
Not cancel, but reshape, and be stricter for children, older people and anyone with a health condition. Move outdoor sights to before 09:00 and after 17:00, and fill the middle of the day with museums, shopping and rest. On a Special Heat Stroke Alert day, keep outdoor time to short, essential trips.
Is July or August worse?
Both are hot; late July to mid-August is usually the peak of the heat and of domestic holidays. Early June and late September are still warm but much easier. The rainy season (tsuyu) in June and early July adds humidity.
Are children and older travellers at greater risk?
Yes. Children are closer to hot pavements and lose fluid faster, and older people sense thirst and heat less. Our own cautious rule of thumb, not an official one: plan as if the WBGT were one band higher. Plan more indoor time and check they're drinking.
Where can I cool down for free?
Department stores, station buildings, convenience stores for a few minutes, libraries and designated cooling shelters. Shrines and parks have shade but rarely air conditioning.
Related decision guides
Official pages for this guide
The rules in this guide come from the official pages below. Japan, Booked. does not book or submit requests on your behalf.
- Ministry of the Environment, heat illness prevention information (English)
- Suginami City, 2026 heat alert operation
- Kyoto Prefecture, WBGT and daily-life guidelines
- Fire and Disaster Management Agency, heatstroke ambulance data
- Fire and Disaster Management Agency, #7119 implementation areas
- Kyoto Prefecture, Kyoto Emergency Advice Center (#7119)
- Japan Meteorological Agency, summer (June–August) 2025 climate summary
- Fire and Disaster Management Agency, heatstroke ambulance cases May–September 2025 (confirmed)
- Chiba Prefecture, cooling shelters (2024)
- Kyoto City, cooling shelters and lists
- Kyoto Prefecture, cooling shelters and 2026 alert period
- Japan Tourism Agency, Safety tips app leaflet
- Ministry of the Environment, "Drink water for health" campaign
- 7-Eleven Japan, own-brand drinks
- Create SD online, OS-1 500 ml
- Yodobashi.com, salt tablets 81 g
- Yodobashi.com, Bioré cooling sheets 20
Read next
- Eating well and cheaply from Japanese convenience storesWhat to buy at 7-Eleven, FamilyMart and Lawson for each meal, how heating and eat-in tax work, allergen labels, and a real-price daily budget.
- Buying cold, fever and pain medicine in Japan: drugstores, labels and limitsWhat to buy for a cold, fever, pain or hay fever in Japan, how to read 第1類/第2類 labels, and the 2026 rules on codeine and pseudoephedrine.
- Check your Japan hotel room’s air conditioning and smoking termsCheck heating/cooling controls, room temperature flexibility, non-smoking policy, and cancellation/change rules before booking your room.
- An Okinawa itinerary for rain and hot weatherPlan shorter outings, rest stops and transport alternatives for days when the weather changes your plans.
- Emergency numbers and visitor help in JapanFind the right emergency contact or help desk, and know what details to have ready when you reach out.
Sources and how this guide was checked
Published · Based on official sources · no affiliate links
Official sources
These official sources explain the rules and conditions used in this guide. Live availability and your own booking, admission or service outcome still need to be confirmed for your trip.
- Ministry of the Environment, heat illness prevention information (English)
What this confirms: Background source checked for this guide.
Last checked - Suginami City, 2026 heat alert operation
What this confirms: Supports the key facts on: 2026 alert season; Heat Stroke Alert threshold and timing; Special Heat Stroke Alert.
Last checked - Kyoto Prefecture, WBGT and daily-life guidelines
What this confirms: Supports the key facts on: WBGT daily-life bands.
Last checked - Fire and Disaster Management Agency, heatstroke ambulance data
What this confirms: Background source checked for this guide.
Last checked - Fire and Disaster Management Agency, #7119 implementation areas
What this confirms: Supports the key facts on: #7119 coverage.
Last checked - Kyoto Prefecture, Kyoto Emergency Advice Center (#7119)
What this confirms: Supports the key facts on: Kyoto #7119.
Last checked - Japan Meteorological Agency, summer (June–August) 2025 climate summary
What this confirms: Supports the key facts on: Summer 2025 temperature.
Last checked - Fire and Disaster Management Agency, heatstroke ambulance cases May–September 2025 (confirmed)
What this confirms: Supports the key facts on: Heatstroke ambulance cases, May–September 2025.
Last checked - Chiba Prefecture, cooling shelters (2024)
What this confirms: Background source checked for this guide.
Last checked - Kyoto City, cooling shelters and lists
What this confirms: Supports the key facts on: Cooling shelters.
Last checked - Kyoto Prefecture, cooling shelters and 2026 alert period
What this confirms: Supports the key facts on: 2027 alert season.
Last checked - Japan Tourism Agency, Safety tips app leaflet
What this confirms: Background source checked for this guide.
Last checked - Ministry of the Environment, "Drink water for health" campaign
What this confirms: Background source checked for this guide.
Last checked - 7-Eleven Japan, own-brand drinks
What this confirms: Background source checked for this guide.
Last checked - Create SD online, OS-1 500 ml
What this confirms: Background source checked for this guide.
Last checked - Yodobashi.com, salt tablets 81 g
What this confirms: Background source checked for this guide.
Last checked - Yodobashi.com, Bioré cooling sheets 20
What this confirms: Background source checked for this guide.
Last checked
About this guide
How Japan's heatstroke alerts and WBGT work, when to sightsee in summer, what to buy at konbini and drugstores, and when to call #7119 or 119.
Checked against Ministry of the Environment, Japan Meteorological Agency, Fire and Disaster Management Agency and prefectural sources on 11 October 2026. Japan, Booked. is independent and this page has no affiliate links.
How we checked this
Sources and limits of this guide
These dated notes show what each source supports, and what you still need to check yourself.
If columns are cut off, scroll sideways. Keyboard: focus the table, then use Left/Right Arrow keys.
| Question | What we found | Where it comes from | What this means for your trip |
|---|---|---|---|
| 2026 alert season | 22 April to 21 October 2026 | Suginami City, 2026 heat alert operation | Checked 11 October 2026. Recheck before you rely on it. |
| Heat Stroke Alert threshold and timing | WBGT 33 at any point in the forecast area; 17:00 day before and 05:00 on the day | Suginami City, 2026 heat alert operation | Checked 11 October 2026. Recheck before you rely on it. |
| Special Heat Stroke Alert | WBGT 35 at all points; 14:00 day before | Suginami City, 2026 heat alert operation | Checked 11 October 2026. Recheck before you rely on it. |
| WBGT daily-life bands | 31+ danger; 28–31 severe warning; 25–28 warning; under 25 caution | Kyoto Prefecture, WBGT and daily-life guidelines | Checked 11 October 2026. Recheck before you rely on it. |
| Summer 2025 temperature | +2.36°C above the reference value, hottest summer since 1898 | Japan Meteorological Agency, summer (June–August) 2025 climate summary | Checked 11 October 2026; JMA. Recheck before you rely on it. |
| Heatstroke ambulance cases, May–September 2025 | 100,510 (confirmed), most since 2008 | Fire and Disaster Management Agency, heatstroke ambulance cases May–September 2025 (confirmed) | Checked 11 October 2026; FDMA, 29 October 2025. Recheck before you rely on it. |
Based on official sources, linked below.
Guide updates Reviewed
When this guide was checked and what changed
- First published
- Last checked
- Check again by
- What we checked
- Ministry of the Environment, Suginami City, Kyoto Prefecture, Fire and Disaster Management Agency, Japan Meteorological Agency, Chiba Prefecture, Kyoto City, Japan Tourism Agency, 7-Eleven Japan, Create SD online and Yodobashi.com, checked 11 October 2026.
- Latest update
- : First published: how hot Japan gets, heatstroke alerts and the heat index, when to be outdoors, what to buy, cooling shelters and when to call 119, checked against official pages on 11 October 2026.
The date above reflects when these checks were last run. If an individual source was rechecked later, you’ll see that date next to it below. Other copy edits are listed in the update history.
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Japan, Booked. is run and edited from Japan. The same editor checks the Japanese and English sources, writes the traveller-facing guidance and keeps the correction history up to date.
What changed
Update history
- First published
First published: how hot Japan gets, heatstroke alerts and the heat index, when to be outdoors, what to buy, cooling shelters and when to call 119, checked against official pages on 11 October 2026.
If an operator, organiser or product changes in a way that affects the guide, we check it again sooner. Reader reports help us spot what to investigate, and we verify them against current official information before publishing. Read our update and corrections policy. See every guide's review schedule. Suggest an improvement to this guide.