Tokyo in Japan's record heat spell: heatstroke alerts, 40C days and what visitors should change

What happened

Japan is in the middle of one of the most severe heat spells in its recorded history, and Tokyo is squarely inside it. In late July, temperatures reached at least 40C (104F) for five consecutive days in parts of the country, the longest such streak Japan has ever recorded, and heatstroke alerts have repeatedly covered large portions of the archipelago, CNN reported on 4 August 2026. The Japan Meteorological Agency introduced a new official designation this summer for days that reach 40C, translating roughly as a "cruelly hot day", because such days have become frequent enough to need their own category.

The clearest illustration of how hard this heat is biting came from a Tokyo zoo. The Tama Zoological Park in Hino city, in the greater Tokyo metropolis, closed its lion exhibit in late July after several of its big cats began showing loss of appetite and fatigue. Ten lions were treated with water sprays, industrial fans, intravenous fluids and medication. Three of them died within a week: a three year old female, Mugi, on 28 July, an eleven year old, Ichigo, three days later, and a fifteen year old, Luena, on Sunday 2 August. Preliminary findings showed dehydration and multiple organ failure in all three. Four more lions are recovering and three remain unwell. If air conditioned animal enclosures with round the clock veterinary care could not keep pace with this heat, an unacclimatised visitor walking Asakusa at 2pm is not going to fare well either.

The heat is compounding a separate emergency in the southwest. A magnitude 7.1 earthquake struck Kumamoto prefecture on the island of Kyushu on 28 July. Kumamoto recorded its highest ever temperature on Monday 3 August while more than 8,500 people were still in emergency shelters and tens of thousands of households remained without running water, according to NBC News, which put the figure at more than 40,000 households citing public broadcaster NHK. A woman in her seventies was found dead of suspected heatstroke while sheltering in her car after the quake, bringing the disaster's death toll to 38. Prime Minister Sanae Takaichi said the government was ensuring a continuous supply of water to evacuation centres, welfare facilities and medical facilities, and Kumamoto governor Takashi Kimura urged displaced residents to run car air conditioning or move to cooled evacuation centres.

The same weather system is driving records across East Asia. South Korea recorded 42.5C in Yangsan on 2 August, its highest in 122 years of observation, and Seoul was placed under its first ever severe heat wave warning on 4 August, as Deutsche Welle reported. Forecasters expect temperatures to fluctuate over the coming days but see no widespread or lasting break from the heat.

Why it matters for travelers

Tokyo is open and functioning normally. Trains are running, attractions are open, there is no advisory against travel and no disruption to arrivals at Haneda or Narita. The risk here is entirely physiological, and it is easy to underestimate because Tokyo does not feel like a dangerous place to walk around.

Humidity is what makes Japanese heat different from dry heat of the same reading. At Tokyo's summer humidity levels, sweat evaporates poorly, so the body's main cooling mechanism works at reduced efficiency and the perceived temperature runs well above the number on the forecast. Visitors arriving from northern Europe or North America are typically not acclimatised, and acclimatisation takes roughly a week to ten days. The first three days of a trip are the highest risk window, which is exactly when most people schedule their most ambitious sightseeing.

The classic Tokyo itinerary is heavily outdoor. Sensoji temple and the Nakamise approach in Asakusa, the Meiji Jingu forest paths, Shibuya crossing and the surrounding streets, Ueno Park, the Imperial Palace East Gardens, Yanaka, Kappabashi and the Toyosu and Tsukiji market areas are all walked, often with long stretches between shade. Add the standard day trips and the exposure increases: Kamakura and its Daibutsu, Nikko, Hakone, and above all Mount Fuji, where the climbing season is underway and where heat, altitude and exertion combine badly.

Japan's heatstroke hospitalisation figures each summer run heavily toward people over 65, and a large share of cases occur indoors rather than outdoors, usually where air conditioning is not being used. For travelers this translates into two specific warnings: do not skip air conditioning overnight to save on a bill in a rental, and check on older travelling companions rather than assuming they will say something.

What to do

Use the Japanese heatstroke alert system. The JMA and Ministry of the Environment issue heatstroke alerts by prefecture based on the WBGT index, which accounts for humidity and radiant heat rather than air temperature alone. When an alert is issued for Tokyo, the official guidance is to avoid non essential outdoor activity, use air conditioning without hesitation and cancel outdoor exercise. The JMA site has English pages, and most Japanese weather apps show the WBGT reading. That number, not the air temperature, is the one to plan around.

Front load and back load the day. Temples open early and are at their best before 9am, when Sensoji and Meiji Jingu are also far less crowded. Take the middle of the day indoors and go back out after 6pm, when Tokyo's night culture is the main event anyway. Shinjuku, Golden Gai, Shimokitazawa and the izakaya alleys under the tracks in Yurakucho are evening destinations by nature.

Move through the underground and connected city. Tokyo's subway, station complexes and the passages that link them are air conditioned, and large parts of Shinjuku, Tokyo Station, Otemachi and Ikebukuro can be crossed without going outside. Department store basements, the depachika food halls, are cool and are a genuine attraction in their own right. Museums are the reliable middle of the day plan: the Tokyo National Museum in Ueno, the Edo Tokyo Museum, teamLab, the Ghibli Museum if you booked ahead, and the Mori Art Museum.

Buy the local heat kit on arrival. Any convenience store or drugstore sells cooling body sheets, neck coolers, portable fans, salt candies and electrolyte drinks such as Pocari Sweat and OS-1, the latter being an oral rehydration solution used medically. Vending machines are on almost every block and stock cold drinks for around 150 yen. Frozen drink bottles double as ice packs against the neck and wrists.

Drink on a schedule, not on thirst. Thirst lags behind dehydration, particularly in humidity. Aim for regular small amounts through the day and include salt, because plain water across a heavy sweating day can leave you low on sodium. Beer is not hydration, and the combination of a hot afternoon and an evening of drinking is a common route to a bad night.

Rethink the ambitious plans. Mount Fuji in these conditions requires real caution: check hut availability, carry far more water than usual, and be honest about turning back. Kamakura and Nikko involve long outdoor walks with limited shelter. Theme parks, Tokyo Disney Resort in particular, mean hours of queuing outdoors and are the single most common place visitors get into trouble in a Japanese heat wave. If you go, use the indoor attractions during peak hours and take the shows and parades as rest stops.

If you are heading to Kyushu, reconsider the timing. Kumamoto is dealing with earthquake recovery, thousands of people in shelters, water outages and record heat at the same time. Aftershocks remain possible. This is not the moment for discretionary travel to the affected area, and travelers already in the region should follow local authority instructions and check accommodation status before arriving. Other parts of Kyushu are less affected, but confirm before you go.

Know the emergency response. Call 119 for an ambulance in Japan. Heat exhaustion presents as dizziness, heavy sweating, headache, nausea, muscle cramps and weakness, and the response is shade or air conditioning, cooling the neck, armpits and groin, and rehydrating. Heat stroke, which involves confusion, hot skin, a very high body temperature or collapse, needs an ambulance immediately. Japan Visitor Hotline on 050-3816-2787 offers 24 hour English support and can direct you to hospitals that treat foreign patients. Travel insurance matters because Japanese emergency care is billed to visitors.

How this fits Tokyo's wider safety picture

Tokyo scores 94 out of 100 in Kakapo's safety assessment, one of the highest scores of any major city in the world. Violent crime is very rare, lost property is routinely returned, the transport network is safe at any hour, and solo travel including solo female travel is about as low friction as it gets anywhere. Almost every hazard a traveler in Tokyo actually faces is environmental rather than criminal: earthquakes, typhoons in late summer, and heat.

That framing is the right way to read this event. Tokyo has not become dangerous. It has entered a stretch of weather in which the ordinary rhythms of a sightseeing trip, several hours of walking with a break for lunch, carry a real physical cost. The infrastructure to manage it is excellent and it is mostly free to use: air conditioned trains, cooled public buildings, vending machines everywhere, alerts published in English. The visitors who get hurt in Japanese heat waves are overwhelmingly the ones who did not change anything about their plans.

Heat of this intensity is also not a one summer anomaly. Japan created a new weather designation this year because 40C days keep arriving, and travelers planning future summer trips should treat July and August in Japan as a season that needs an itinerary built around the heat rather than one that ignores it.

The bottom line

Japan is in a record heat spell with no lasting break in sight, and heatstroke alerts are repeatedly covering Tokyo and much of the country. The city is open and safe to visit, but a normal outdoor itinerary is not safe to run in the middle of the day. Sightsee early and late, use the subway, department stores and museums during peak heat, drink electrolytes rather than water alone, watch the WBGT based heatstroke alert rather than the air temperature, and call 119 without hesitating if someone becomes confused or stops sweating. Travelers with Kyushu plans should look closely at the Kumamoto earthquake recovery before going.