Japan's Summer Heat: Staying Safe While Sightseeing

How hot is too hot? Use WBGT, not temperature alone#

Japan’s summer is not just hot — it is humid. Humidity makes sweat less effective at cooling the body, while direct sun and weak wind add more heat stress. Air temperature therefore does not tell the whole story.

Japan’s official measure is WBGT (Wet Bulb Globe Temperature), which combines temperature, humidity, radiant heat, and wind. As of July 2026, use the Ministry of the Environment’s official English Heat Stroke Alert and WBGT map for the place and hour you will be outside.

WBGT	Official risk band	Practical sightseeing decision (as of July 2026)
Below 21	Almost safe	Keep normal hydration; risk is not zero if you are unwell or exerting yourself
21–25	Caution	Drink regularly and notice whether the route has indoor stops
25–28	Warning	Add frequent rests; for strenuous activity, break at least every 30 minutes
28–31	Severe warning	Avoid strenuous outdoor activity and shorten outdoor segments
31 or higher	Danger	Avoid outdoor exercise; make the itinerary mostly air-conditioned

WBGT can change by hour and location. A shaded park, an exposed queue, and an underground concourse can have different conditions even within the same city.

What are the warning signs, and when do I call for help?#

Heat illness can start mildly and get worse fast. The most important rule: if someone collapses, cannot answer clearly, has a seizure, or cannot drink by themselves, call 119 immediately and ask for an ambulance (kyukyusha). Do not wait.

This table shows common signs and what to do. It is general guidance, not medical advice — if you are unsure, treat it seriously.

Signs	How serious	What to do
Heavy sweating, thirst, tiredness	Early warning	Move to shade or AC, drink water, rest
Dizziness, headache, muscle cramps, nausea	Getting worse	Stop activity, cool the body, sip water with salt; if no improvement, seek medical help
Confusion, fainting, seizure, inability to drink	Emergency	Call 119 now; move to a cool place, loosen clothing, and cool the body while waiting

The emergency number for an ambulance and fire in Japan is 119 (police is 110). On the call, you can say “kyukyusha” for ambulance. Some areas have English support or interpreter help.

If you feel unwell at any point, stop, find a cool place, rest, and cool down. Do not push through to finish a sightseeing plan. Do not force oral fluids if the person is not fully alert or cannot swallow.

Where can I cool down while sightseeing?#

Plan indoor breaks before leaving, rather than searching only after someone feels ill. A designated cooling shelter is the clearest option when open; ordinary businesses and station platforms are not guaranteed rest spaces.

Place	Cost	Notes (as of July 2026)
Designated cooling shelters	Free	Municipal facilities opened under local rules; check the city or ward list
Large stations or underground concourses	Usually free	Some areas are cool, but outdoor platforms and small stations may not be
Shopping malls and department stores	Free to enter	Strong AC, seating, restrooms
Public libraries and city facilities	Free	Quiet, cool, open to all
Cafes	Price of a drink	Sit and rest out of the heat

For more fallback locations and what is actually open to visitors, use the Japan cool-down spots guide.

How do I check the heat warning before I go out?#

The Ministry of the Environment and JMA jointly issue a Heat Stroke Alert when the forecast WBGT is 33 or higher at any observation point in one of Japan’s 58 forecast regions. As of July 2026, the official English alert map is updated at about 5:00 p.m. for the next day and 5:00 a.m. for the current day.

The same map separately displays a Special Heat Stroke Alert, a prefecture-level warning for exceptional heat that could cause serious health harm. Treat it as a reason to move or cancel outdoor plans, not simply to carry more water.

On an alert day, the safest plan is to:

1. Limit time outdoors, especially in the middle of the day.
2. Stay in cool places and take frequent breaks.
3. Drink often — before you feel thirsty.
4. Watch others in your group, especially children and older travelers, who feel heat strongly.
5. On a special alert day, treat it as a signal to keep sightseeing mostly indoors.

Which numbers should change the day’s plan?#

Topic	Detail (as of July 2026)
Hottest months	July and August; temperatures can exceed 35°C
Better risk measure	WBGT, because it includes humidity, radiant heat, and wind
Emergency number	119 for ambulance (kyukyusha) and fire
Heat Stroke Alert	Forecast WBGT 33+; check the official English map at 5 p.m. and again at 5 a.m.
Special alert	Prefecture-level exceptional heat; move or cancel outdoor plans
Free cool-down spots	Designated cooling shelters, public facilities, and malls with seating
Hydration	Drink before thirst; follow individual medical advice on fluids and salt
If you feel unwell	Rest, cool down, and seek medical help

What are the common mistakes that lead to heat illness?#

A few simple errors put visitors at risk in Japan’s summer. Avoid these:

Mistake	Why it is a problem	Better choice
Looking only at air temperature	It misses humidity, sun, and wind	Check hourly WBGT for the route
Waiting until you feel thirsty	You are already low on fluids	Sip water through the day
Continuing a strenuous route at WBGT 28+	Official guidance says to avoid heavy exercise	Shorten or move the route indoors
Treating a shaded platform as a cool room	Shade may still be hot and humid	Use an air-conditioned indoor stop
Ignoring early signs like dizziness	Heat illness can get worse fast	Stop, cool down, rest right away

Heat illness is serious but largely preventable. Slow down, stay in the shade and AC, drink often, and check the heat alert before heading out.

This page is general guidance, not medical advice. If you feel unwell, rest, cool down, and seek medical help. In an emergency, call 119. Check the official alert map after its 5:00 p.m. and 5:00 a.m. updates before committing to a long outdoor route.