Summer Heat and Heatstroke for Visitors

Japan summer heat and heatstroke are planning realities for any visitor between June and September, when humidity across most of Honshū, Shikoku, Kyūshū, and Okinawa makes outdoor sightseeing physically risky without preparation.¹² A working knowledge of Japan's heat-alert system, early warning signs, and when to call an ambulance can prevent a heat emergency from defining a trip.

Confirm current details with official sources

Fees, rules, and requirements can change. Confirm current details at the Ministry of the Environment heat illness prevention site. This article is general information, not medical advice; consult a licensed physician for your specific health situation, or a pharmacist regarding whether your medications affect heat tolerance or hydration.

Overview

Japan's summer heat is not just high temperatures. It is the combination of heat and humidity that makes conditions dangerous, often on days that look unremarkable by the thermometer alone. The government runs a dedicated alert system from late April through late October, and the record-breaking summers of recent years have made heat-illness prevention a central part of trip planning.¹³

When the heat season runs

Japan's rainy season, 梅雨 (tsuyu, "plum rain"), brings high humidity from roughly late May or early June, with peak heat following from mid-July through late August.¹² Heat can linger into September, and the combination of humidity and warmth makes even cloudy June days uncomfortable.

The Ministry of the Environment's heatstroke alert system operates from 22 April 2026 to 21 October 2026 (as of 2026-04-14; confirm current figures with the Ministry of the Environment).³ Shoulder-month visitors in May or October may also encounter active alerts.³

Regional timing varies. Okinawa and the Amami Islands enter tsuyu first, around early May, followed by Kyūshū, Shikoku, and then Kantō and Kinki in early June. Tsuyu typically ends in the Kantō region around mid-to-late July, after which temperatures peak.¹

Why humidity matters more than the thermometer

In humid conditions, sweat evaporation slows dramatically, limiting the body's primary cooling mechanism.⁴⁵ The Ministry of the Environment's heat-illness prevention manual states directly that air temperature alone cannot assess heat-illness risk in Japan's humid summers.⁵

Cloudy days and lower temperatures can still cause heatstroke

Heatstroke can occur on cloudy days and at air temperatures that feel moderate, because humidity suppresses cooling through sweat evaporation.² Visitors from drier climates consistently underestimate this effect.⁴

The WBGT index (covered in the next section) accounts for this by weighting the wet-bulb (humidity) component at 0.7, making it the dominant factor in the calculation.⁵

Recent record summers

Summer 2025 (June to August) set the record as the hottest summer since Japan Meteorological Agency records began in 1898, with a nationwide average temperature +2.36 degrees C above the long-term norm (as of 2025-09-30).⁶⁷ The previous record, +1.76 degrees C above normal, was shared by 2023 and 2024 as a tie; summer 2025 exceeded it by 0.6 degrees (as of 2025-09-30).⁷

The national record high temperature reached 41.8 degrees C at Isesaki, Gunma Prefecture, on 5 August 2025 (as of 2025-09).⁶ In that same summer, temperatures of 40 degrees C or higher were recorded at 30 locations across 13 prefectures over nine days, the most widespread extreme heat since comparable statistics began in 2010 (as of 2025-09).⁶

Of 153 JMA meteorological stations nationwide, 132 recorded their highest average summer temperature on record in 2025 (as of 2025-09).⁶

As of 4 August 2026, the current season had recorded 4,727 station-days at or above 35 degrees C and 27 station-days at or above 40 degrees C, second only to 2025's pace at the same point (as of 2026-08-07).⁸ JMA has not yet published a final summer 2026 summary.

JMA adopted the term 酷暑日 (kokushobi, "severe heat day") on 17 April 2026 for days when the maximum temperature reaches 40 degrees C or higher (as of 2026-04-17).⁹ It is the first new heat-classification term since 猛暑日 (mōshobi, "extremely hot day," 35 degrees C threshold) was introduced in 2007.⁹

Regional differences

Heat intensity varies sharply across Japan. Kantō and Kinki inland basins, including Tokyo, Kyoto, and inland cities like Kumagaya (Saitama), experience the most intense combination of high temperature and humidity.¹² The Tokai region shares this pattern.

Okinawa is hot but maritime: humidity is extreme, yet maximum temperatures rarely exceed 35 degrees C because ocean air moderates the peaks.¹

Hokkaido is relatively cooler in summer, but it is not immune to heat risk. Nemuro recorded its highest-ever heatstroke ambulance transport count (17 people) in 2023, and since 2021 northern Japan has consistently recorded the highest annual temperature deviations from the long-term norm (as of 2024).¹⁰¹¹

Highland areas such as Karuizawa (Nagano) and Nikkō (Tochigi) remain cooler. These are precisely the locations whose WBGT observation points were excluded from the Special Heatstroke Alert calculation starting in FY2026, because their lower readings did not reflect conditions in the populated lowlands of their prefectures (as of 2026-04-18).¹²

Heat Alerts and the WBGT Index

Japan's heat-warning system is built on the WBGT index and operates through two alert tiers. Both are published in English, and a free app can push alert notifications to a visitor's phone.

What WBGT measures

WBGT (暑さ指数, atsusa shisū; Wet Bulb Globe Temperature) is an index that combines humidity, radiant heat (from the sun and surrounding surfaces), and air temperature into a single number expressed in degrees C.¹³ It is not the same as air temperature.

The outdoor formula is: WBGT = 0.7 x wet-bulb + 0.2 x globe (black-bulb) + 0.1 x dry-bulb temperature. The indoor formula omits the dry-bulb term: 0.7 x wet-bulb + 0.3 x globe.⁵ Humidity dominates because it determines how effectively sweat can cool the body.⁴

The Ministry of the Environment publishes WBGT observed and forecast values for approximately 840 points nationwide during the alert operating season (as of the 2022 manual edition; confirm current figures with the Ministry of the Environment heat illness prevention site).⁵

WBGT daily-life guideline bands

The daily-life guideline, published by the Japanese Society of Biometeorology and cited in the MoE heat-illness prevention manual, uses four bands.⁵¹³ This is the guideline most relevant to visitors planning a sightseeing day.

WBGT	Category	Risk level	Recommended action
31 and above	危険 (kiken, Danger)	Risk in all daily activities	Stay indoors where possible; older adults at high risk even at rest513
28 to under 31	厳重警戒 (genjū keikai, Severe warning)	Risk in all daily activities	Avoid direct sun when outdoors; watch for indoor temperature rise513
25 to under 28	警戒 (keikai, Warning)	Risk in moderate or heavier activity	Take regular rest breaks during exercise or strenuous activity513
Under 25	注意 (chūi, Caution)	Risk in strenuous activity only	Generally low risk, but heat illness can still occur during intense exercise or heavy labor513

A separate exercise guideline from the Japan Sport Association uses five bands, with a sub-21 "almost safe" tier and a stricter 31+ band where "exercise should be prohibited except in special cases."¹⁴ Hikers and visitors planning strenuous outdoor activities should reference the exercise guideline's tighter thresholds.

WBGT	Category	Guidance
31 and above	Danger	Exercise should be stopped; children especially at risk14
28 to 31	Severe warning	Avoid heavy exercise; frequent rest and aggressive hydration14
25 to 28	Warning	Frequent rest and hydration; rest every 30 minutes for heavy exercise14
21 to 25	Caution	Hydrate during exercise14
Under 21	Almost safe	Appropriate hydration still needed14

Neither guideline table is the alert trigger. The Heatstroke Alert and Special Heatstroke Alert (below) use their own, higher thresholds.³

Heatstroke Alert and Special Heatstroke Alert

Japan's alert system has two tiers, established under the Revised Climate Change Adaptation Act.¹⁵ The following comparison reflects the FY2026 rules (as of 2026-04-14).³¹⁶

	Heatstroke Alert (熱中症警戒アラート)	Special Heatstroke Alert (熱中症特別警戒アラート)
Trigger	Forecast daily max WBGT of 33 or higher at one or more observation points in the forecast area	Forecast next-day daily max WBGT of 35 or higher at all WBGT points in the prefecture (excluding designated high-elevation points)
Meaning	Risk of harm to health from heat illness is markedly high	Risk of serious harm to health is especially high
When issued	Around 17:00 the previous day and around 05:00 the same day	Judged on 10:00 forecast of previous day; issued around 14:00 the previous day
Geographic unit	Forecast area (58 areas nationwide; Hokkaido, Kagoshima, and Okinawa are subdivided)	Prefecture
Issuance count	613 (2021), 889 (2022), 1,232 (2023), 1,722 (2024), 1,749 (2025)	In operation since April 2024; never issued as of 2026-03-30

The Special Heatstroke Alert has never been triggered since its creation in April 2024 (as of 2026-03-30).¹⁶ It requires WBGT 35 at every observation point in a prefecture, a threshold so high that even the record-setting summers of 2024 and 2025 did not reach it prefecture-wide.

Starting in FY2026, the Ministry of the Environment excluded 24 high-elevation WBGT observation points in 13 prefectures (including Karuizawa in Nagano and Nikkō in Tochigi) from the Special Heatstroke Alert calculation (as of 2026-03-30).¹⁶¹² These highland stations recorded cooler readings that did not reflect conditions in the populated lowlands. The 35-at-all-points trigger itself is unchanged, and the regular Heatstroke Alert is not affected by this revision.¹⁶

The MoE alert page updates three times daily: around 05:00 (today's alerts), and around 14:00 and 17:00 (tomorrow's alerts) (as of 2026-09).¹⁷

Checking alerts in English

The Ministry of the Environment's English heat illness prevention site displays WBGT forecast and observed values by region.¹⁸

Set up the Safety Tips app before your trip

The Safety Tips app, supervised by the Japan Tourism Agency, sends push notifications for heatstroke alerts, including next-day alerts added in version 3.15.0 (as of 2025-03-24).¹⁹²⁰ The app supports 15 languages and allows setting up to five locations within Japan for alerts (as of 2025-03).²⁰

JMA's website and major weather apps in Japan also display alert status and WBGT forecasts.²

Cooling shelters

A クーリングシェルター (kūringu sherutā, "cooling shelter"), formally called 指定暑熱避難施設 (shitei shonetsu hinan shisetsu, "designated heat-avoidance facility"), is an air-conditioned public or private facility designated by a municipal mayor under the Revised Climate Change Adaptation Act (enacted 1 April 2024).¹⁵²¹

These shelters are legally required to open when a Special Heatstroke Alert is issued for the area.²¹²² Since that alert has never been triggered (as of 2026-03-30), the mandatory-opening provision has not yet been activated nationally.¹⁶ Municipalities may also open shelters under their own local standards even without a Special alert.²¹

Eligible facility types include public buildings (community centers, libraries, welfare centers) and participating private businesses (shopping malls, drugstores, banks).²²¹⁰ Whether a given facility is a designated cooling shelter depends on both the municipality's designation list and the individual establishment's participation. Coverage varies widely:

• Inagi City (Tokyo) designated community centers, cultural centers, libraries, and two private businesses for FY2026 (as of 2026).²²
• Kumagaya (Saitama), one of Japan's hottest cities, designated 30 cooling spaces, 17 of them in private businesses (as of 2026).¹⁰
• Naha (Okinawa) established its first cooling shelter at city hall (as of 2026).¹⁰
• Nemuro (Hokkaido) does not yet have designated cooling shelters (as of 2026).¹⁰

Visitors can check municipal websites for published facility lists. Signage practices vary by municipality.²²

Recognizing Heatstroke

熱中症 (necchūshō, "heat illness") is the general Japanese term for heat illness, encompassing the range from mild heat cramps to life-threatening heatstroke.²³ Japan uses a three-grade severity classification originating from the Japanese Association for Acute Medicine.²³²⁴²⁵

Early warning signs

Grade	Severity	Symptoms	Appropriate response
I (mild)	Manageable with on-site first aid	Dizziness, lightheadedness, muscle cramps, heavy sweating, tingling in hands and feet	Move to a cool place, cool the body, provide oral rehydration2324
II (moderate)	Requires medical attention	Headache, nausea, vomiting, fatigue, impaired judgment, inability to drink independently	Transport to hospital2324
III (severe)	Requires hospitalization and intensive care	High body temperature, loss of consciousness, convulsions, inability to walk straight, unresponsiveness	Call 119 immediately2324

The critical decision point: if consciousness is impaired in any way, the case is Grade II or higher and requires hospital transport.²⁶ Grade I symptoms can escalate to Grade III rapidly if left unaddressed.²³

Signs of a severe case

Confusion, high body temperature (40 degrees C or above), whole-body convulsions, and unresponsiveness signal a Grade III case.²³²⁴ These symptoms mean the body has lost the ability to regulate its own temperature, and the situation is life-threatening without treatment.²³

An inability to independently open a bottle, drink without choking, or perform basic self-care also indicates a case requiring immediate hospitalization.²³

First Response and When to Call 119 or #7119

The Ministry of the Environment's first-aid flow for heat illness follows a decision tree: check consciousness first, cool the body regardless, and escalate based on whether the person can drink and whether symptoms improve.²⁶²³

The following diagram summarizes the decision points, based on the MoE's published first-aid sequence.²⁶²³²⁴

Immediate first aid

Move the person to shade or an air-conditioned space and loosen clothing.²³²⁶ Cool the body by applying cold items (ice packs, frozen bottles, cold water) to areas with large blood vessels: the sides of the neck, armpits, and groin.²³²⁶

Applying cold water to the palms is also effective.²³

If the person is conscious and able to drink, provide cold oral rehydration solution or a sports drink. Do not give plain water alone, because prolonged sweating depletes salt.²³²⁴

If they cannot drink independently, do not attempt to force fluids; call 119.²³²⁶ If symptoms do not improve after cooling and fluid intake, seek medical attention.²⁶

When to call 119

Call 119 (ambulance) when consciousness is affected (confusion, unresponsiveness), when the person cannot drink, or when cooling and fluids bring no improvement.²³²⁶

Ambulance service in Japan is free of charge; there is no fee for the transport itself regardless of the caller's insurance status.²³ Hospital treatment, however, is not free: visitors without Japanese health insurance pay the full uninsured rate (as of 2026; confirm current billing arrangements with the treating hospital or your travel insurer).²³

Call 119 immediately if consciousness is impaired

Impaired consciousness means the body can no longer regulate its temperature. Call 119, begin cooling, and do not wait to see if the person improves on their own.²³²⁶

For the mechanics of calling 119, including how to communicate with a Japanese-speaking dispatcher, see Emergency Numbers in Japan: 110 and 119, and the Language-Barrier Reality of Calling Them.

#7119 and where it is available

#7119 (救急安心センター事業, kyūkyū anshin sentā jigyō, "Emergency Consultation Center service") is a non-emergency medical telephone consultation service where doctors, nurses, and other specialists assess whether an ambulance is needed.²⁷

This is not a nationwide universal service. Availability, operating hours, and coverage vary by prefecture and municipality (as of 2026-07).²⁷ The Fire and Disaster Management Agency maintains a list of implementing regions.

Some regions operate 24/7, while others run only on evenings, weekends, and holidays (as of 2025).²⁷

Language support on #7119 is primarily in Japanese. English availability has not been confirmed by a primary source and should not be relied upon.²⁷

Getting help without Japanese

Ask station staff, a hotel front desk, or コンビニ (konbini, "convenience store") staff to call on your behalf. They can communicate in Japanese with the 119 dispatcher.¹

The Japan Visitor Hotline (JNTO) operates 24 hours, 365 days, in English, Chinese, and Korean. It provides support for emergencies (accidents, illness), natural disasters, and general tourist information. The domestic number is 050-3816-2787 (as of 2026).²⁸

Paying for treatment

Visitors pay out of pocket at hospitals in Japan; national health insurance does not cover short-term visitors.²³ Hospitals and Clinics for Tourists: English-Speaking Options and How Billing Works covers how billing works and where to find English-speaking facilities, and Why Travel Insurance Genuinely Matters in Japan covers the case for carrying coverage.

Hydration and Cooling Supplies

Prevention depends more on steady hydration and accessible cooling than on toughness or heat tolerance. Japanese convenience stores and drugstores stock a full range of summer-specific supplies.

Sports drinks versus oral rehydration solution

Sports drinks such as Pocari Sweat and Aquarius are widely available at konbini, vending machines, and supermarkets. They contain electrolytes and sugar and are suitable for maintaining hydration during activity, as a prevention measure.²³¹

OS-1 (オーエスワン), manufactured by Otsuka Pharmaceutical Factory, is an oral rehydration solution (経口補水液, keikō hosui eki, "oral rehydration solution") classified as a food for persons with medical conditions and formulated following WHO oral rehydration therapy guidelines.²⁹ It is designed for treating dehydration that has already begun, not for routine hydration, and is indicated when heatstroke symptoms such as cramps, nausea, or excessive perspiration are present.²⁹

OS-1 is sold at pharmacies and drugstores in Japan, not typically at convenience stores (as of 2026; confirm current availability with local pharmacies or drugstores).²⁹ For locating a pharmacy, see Finding a Pharmacy in Japan: What's Available Over-the-Counter (and What Isn't).

The key distinction: sports drinks prevent dehydration during activity; OS-1 treats dehydration that has already set in.²⁹²³

Salt supplements and snacks

Salt candy (塩飴, shio ame, "salt candy") and salt tablets are sold at konbini and drugstores in summer, often near the register.¹²⁴ When prolonged sweating depletes the body's salt reserves, water alone is not enough to restore the balance.²³

When sports drinks or salt supplements are unavailable, a simple saline solution (1 to 2 grams of salt per liter of water) is also effective.²⁶

Cooling gear sold locally

Konbini and drugstores stock a range of cooling goods throughout summer.¹

• Neck coolers (reusable gel types and disposable types)
• Cooling sprays and cold sprays
• Body-cooling wipes
• Portable fans (handheld and USB-powered)
• Parasols (日傘, higasa, "sun umbrella") and wide-brimmed hats

Staying supplied on the move

Vending machines are common in urban Japan, providing beverage access near stations and commercial areas.¹ They thin out significantly at shrines, temple grounds, hiking trails, and rural sites. Carry a bottle and refill before moving to areas with limited access.¹

Public trash bins are scarce in Japanese cities. Carry used bottles until a bin is available, or return them to a konbini. For context on why bins are hard to find, see Why It's So Hard to Find a Public Trash Can in Japan.¹

Pacing an Itinerary Around the Heat

Adjusting the shape of a sightseeing day is the single most effective heat-illness prevention measure available to visitors. It costs nothing and requires no equipment.

Shift outdoor sightseeing to early and late hours

GO TOKYO advises "avoiding the daytime heat and sightseeing from the evening into the night" during summer.¹ The Ministry of the Environment's daily-life guideline for WBGT 31+ states: "avoid going out where possible and move to a cool room."⁵

A practical pattern: visit temples, gardens, and parks early in the morning before the midday heat builds, shift to indoor activities during the hottest hours, and return outdoors for late-afternoon or evening walks.¹ The MoE also recommends adjusting gradually to the heat rather than pushing through it.³⁰

Indoor refuges near major stations

Major stations across Japan sit within reach of air-conditioned alternatives: museums, department stores, underground shopping malls (地下街, chikagai, "underground mall"), and covered shopping arcades (商店街, shōtengai, "shopping arcade").¹ These serve both as sightseeing destinations and as cooling breaks.

For a framework on structuring how much ground a single day can realistically cover, see How Many Things Can You Actually Do in a Day? A Realistic Pacing Framework.

High-exposure sites and activities

Gravel temple grounds (Kyoto's major temples are a common example), long outdoor queues, theme parks, and open-air festival viewing all carry elevated heat risk due to prolonged sun exposure and limited shade.¹²

Outdoor summer festivals run through the peak heat months. See Summer Matsuri Season: What to Expect and How to Plan Around It and Hanabi (Fireworks) Festivals: Japan Summer-Night Spectacle for planning around these events.

Cooler alternatives in midsummer

Hokkaido and highland areas (Karuizawa, Nikkō, the Kawaguchiko area) offer relatively cooler summer temperatures and can serve as an alternative base or a mid-trip break from the heat.¹ This is a regional climate difference, not a universal claim about Japan's summer being mild. See Hokkaido's Inverted Seasonal Calendar for how Hokkaido's seasons differ from the rest of Japan.

Even Hokkaido is warming. Since 2021, northern Japan has consistently recorded the highest annual temperature deviations from the long-term norm, and heat-related ambulance transports have reached record levels in traditionally cool cities (as of 2024; confirm current regional patterns with the Japan Meteorological Agency).¹¹¹⁰ Cooler does not mean cool enough to ignore heat precautions entirely.

Higher-Risk Travelers

Heat-illness risk is not evenly distributed. Age, acclimatization status, exertion level, and certain medications all shift the threshold at which symptoms appear.

Older travelers

Adults aged 65 and over accounted for 57.1% of all heatstroke ambulance transports in 2025 (57,433 of 100,510 total) (as of 2025-10-29; confirm current statistics with the Fire and Disaster Management Agency).³¹³² Over the 2010 to 2024 period, the 65+ age group averaged 50.7% of all transports (as of 2024).¹¹

In the week of 13 to 19 July 2026 (10,857 transports that week), seniors represented 62.0% of cases (as of 2026-07).³³

Older adults tend to sweat less and have weaker thirst signals, making them prone to dehydration even when they feel fine.²⁵²³

Some medications increase vulnerability to heat illness

Common medications, including diuretics, blood-pressure medications, and heart medications, can impair the body's ability to regulate heat.²⁵ If you or a travel companion take any of these, consult a physician or pharmacist before traveling in Japan's summer about how to manage heat exposure.

Babies and children

Children's thermoregulatory functions are not yet fully developed. They have a larger surface area relative to body weight, which causes them to overheat faster than adults.²⁵

Children in strollers are closer to sun-baked pavement. Temperatures inside a stroller can exceed 30 degrees C even when air temperature is only 27 degrees C.²⁵ Children also have difficulty voicing that they are hot or feeling unwell; watch for flushed faces, lethargy, and reduced sweating.²⁵

For logistics specific to traveling with small children, see Traveling with Babies and Toddlers: Strollers, Nursing Rooms, and Supplies and A Family-with-Kids Japan Itinerary Framework.

Hikers and Mount Fuji climbers

Hikers face compounded risk: exertion plus sun exposure plus distance from medical help.¹ When a Heatstroke Alert covers the hiking area and the WBGT forecast reaches the danger band (31+), consider canceling or rerouting the hike.¹⁴

Trailhead shops and mountain huts may be the last chance to buy drinks before a long stretch without supply.¹ For trail logistics, see Hiking in Japan: Trail Grades, Seasons, and Mountain Huts. For the current access rules on Japan's most-climbed mountain, see Mount Fuji Climbing Restrictions: Time Bands, Capacity Caps, and Mandatory E-Learning.

Visitors from cooler or drier climates

暑熱順化 (shonetsu junka, "heat acclimatization") is the body's physiological adaptation to heat, including increased blood volume, earlier onset of sweating, and more efficient thermoregulation.³⁴ Full acclimatization begins within days of regular exposure and reaches completion in approximately two weeks.³⁴

Acclimatization is temporary: pronounced loss begins after four days without heat exposure, with complete loss within three to four weeks.³⁴

For visitors arriving from a cool or dry climate, the first two to three days in Japan carry the highest risk. Plan shorter outdoor blocks during this period and build up gradually.³⁴ The Ministry of the Environment recommends adjusting to heat without pushing through it.³⁰

Good to know

Heat illness also happens indoors and at night

Indoor settings (mainly homes and accommodation) accounted for 39.9% of all heatstroke ambulance transports, averaged across 2017 to 2024, making it the single most common location category (as of 2024; confirm current statistics with the Fire and Disaster Management Agency).¹¹ In the week of 13 to 19 July 2026, residences accounted for 41.7% of transports, followed by streets at 21.4% (as of 2026-07).³³

A 熱帯夜 (nettaiya, "tropical night") is a JMA-classified night when the minimum temperature does not fall below 25 degrees C.⁹ These are frequent in Tokyo and Osaka during July and August, disrupting sleep and accumulating heat fatigue across a trip.¹ Keep accommodation air-conditioned overnight; do not turn off AC to save on electricity in midsummer.¹

The heat season starts earlier than many visitors expect

The MoE alert operating period begins in late April.³ June, before the rainy season ends, already carries high humidity and meaningful heat risk. In 2025, June set the monthly record for heatstroke ambulance transports, with 17,229 people transported (as of 2025).³²³

Alerts are local, so check where you are going

Heatstroke Alerts are issued per forecast area (58 areas, roughly prefecture-level).³ A day trip into a neighboring prefecture can carry a different alert status than where you are staying. Check the alert for your destination each morning, not just for your hotel's city.³

Alcohol, caffeine, and festival drinking

Alcohol has a diuretic effect and accelerates dehydration. Caffeinated beverages also have a mild diuretic effect and should not be relied on as the primary hydration source.²⁴

At beer gardens and matsuri (summer festivals), alternate alcoholic drinks with water or sports drinks.²⁴

Summer overlaps with typhoon season

Japan's peak heat months coincide with typhoon season. A typhoon can disrupt travel plans, alter weather patterns, and arrive with limited lead time during the same months when heat is highest. For how to prepare for and respond to typhoons, see Typhoon Season and Tsunami Awareness for Visitors.

Pack for heat before you fly

Breathable, light-colored, loose clothing, a hat or parasol, and a refillable water bottle are the basics.¹ Konbini and drugstores in Japan stock neck coolers, cooling sprays, and parasols starting in early summer, but popular items can sell out during heat waves.¹ For a full packing checklist, see What to Pack for Japan: Weather, Footwear, and Cash-Carrying Norms.

See also

• Off-Season and Shoulder-Season Travel: The Value Case for Visiting Japan Outside Peak
• Golden Week and Obon: The Domestic-Travel-Crowding Weeks to Plan Around

References

Footnotes

1. GO TOKYO. "Can you sightsee comfortably even in the hot summer?". https://www.gotokyo.org/en/plan/heat-safety-tips/index.html ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴

2. Kyoto Travel. "How to Avoid Heatstroke While Traveling in Japan". https://kyoto.travel/en/news/avoid-heatstroke-while-traveling-in-japan/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

3. 環境省 (Ministry of the Environment). 「令和８年度熱中症特別警戒アラート及び熱中症警戒アラートの運用を開始します」 (press release, 2026-04-14). https://www.env.go.jp/press/press_04076.html ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹

4. Ministry of the Environment Heat Illness Prevention Information site (English). "All about WBGT". https://www.wbgt.env.go.jp/en/wbgt_lp.php ↩ ↩² ↩³

5. 環境省 (Ministry of the Environment). 『熱中症環境保健マニュアル2022』 chapter I-6 「暑さ指数（WBGT）：熱中症予防のための指標」 (PDF). https://www.wbgt.env.go.jp/pdf/manual/heatillness_manual_1-6.pdf ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹

6. Nippon.com. "Japan Endures Hottest Summer on Record in 2025". https://www.nippon.com/en/japan-data/h02524/ ↩ ↩² ↩³ ↩⁴

7. Science Japan (JST). "This summer was 2.36 degrees above average, updating the record for hottest summer". https://sj.jst.go.jp/stories/2025/s1027-01p.html ↩ ↩²

8. Nippon.com. "Tracking Japan's High-Temperature Days in 2026". https://www.nippon.com/en/japan-data/h02863/ ↩

9. Nippon.com. "Severe Heat: Japan Adopts Official Name for No Longer Uncommon 40 C Days". https://www.nippon.com/en/japan-data/h02769/ ↩ ↩² ↩³

10. Japan Times Special Features. "From Naha to Nemuro, how Japan's cities are responding to more heat". https://features.japantimes.co.jp/japanese-cities-heat-action-plans/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

11. PMC / Scientific Reports. "Nationwide analysis of cases of emergency transport due to heatstroke in Japan from 2010 to 2024". https://pmc.ncbi.nlm.nih.gov/articles/PMC13473147/ ↩ ↩² ↩³ ↩⁴

12. 時事通信 (Jiji Press). 「熱中症アラート、２２日運用開始 特別警戒の基準見直し―環境省」 (2026-04-18). https://www.jiji.com/jc/article?k=2026041800130&g=soc ↩ ↩²

13. 環境省熱中症予防情報サイト. 「暑さ指数(WBGT)について」. https://www.wbgt.env.go.jp/wbgt.php ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

14. Ministry of the Environment Heat Illness Prevention Information site (English). "WBGT Guideline". https://www.wbgt.env.go.jp/en/wbgt.php ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷

15. 環境省熱中症予防情報サイト. 「改正気候変動適応法」 page. https://www.wbgt.env.go.jp/doc_ccaa.php ↩ ↩²

16. 環境省 熱中症対策室 (Ministry of the Environment, Heat Illness Countermeasures Office). 「熱中症特別警戒情報に係る発表基準の変更に伴う電子情報提供サービスへの影響について」 (notice PDF, 2026-03-30). https://www.wbgt.env.go.jp/pdf/notice/20260330_notice.pdf ↩ ↩² ↩³ ↩⁴ ↩⁵

17. 環境省熱中症予防情報サイト (MoE Heat Illness Prevention Information site). 「熱中症警戒アラート」 page. https://www.wbgt.env.go.jp/alert.php ↩

18. 環境省熱中症予防情報サイト (English). "Heat Illness Prevention Information". https://www.wbgt.env.go.jp/en/ ↩

19. JNTO / Japan Tourism Agency. "Safety tips" app page (English). https://www.jnto.go.jp/safety-tips/eng/app.html ↩

20. Safety Tips app, Apple App Store listing. https://apps.apple.com/us/app/safety-tips/id858357174 ↩ ↩²

21. 環境再生保全機構 (ERCA). 「指定暑熱避難施設について」. https://www.erca.go.jp/heatstroke/shonetsu/ ↩ ↩² ↩³

22. Inagi City (English). "Please use the cooling shelter as a heatstroke prevention measure". https://www.city.inagi.tokyo.jp/en/kenko/iryou_kenkou/1003022/1012273.html ↩ ↩² ↩³ ↩⁴

23. Nippon.com. "A Heatstroke Prevention and Treatment Guide for Japan's Humid Summers". https://www.nippon.com/en/guide-to-japan/gu050001/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰ ↩¹¹ ↩¹² ↩¹³ ↩¹⁴ ↩¹⁵ ↩¹⁶ ↩¹⁷ ↩¹⁸ ↩¹⁹ ↩²⁰ ↩²¹ ↩²² ↩²³ ↩²⁴ ↩²⁵

24. Fun! Japan. "What Are the Symptoms of Heatstroke? Remedies, Preventive Items, and Alert Systems". https://www.fun-japan.jp/en/articles/14093 ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰

25. Japan Times Special Features. "How to prevent and respond to heatstroke in Japan this summer". https://features.japantimes.co.jp/heatstroke-explainer/ ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶

26. 環境省 (Ministry of the Environment). 『熱中症環境保健マニュアル2022』 chapter II-3 「熱中症を疑ったときには何をするべきか」 (PDF). https://www.wbgt.env.go.jp/pdf/manual/heatillness_manual_2-3_2-4.pdf ↩ ↩² ↩³ ↩⁴ ↩⁵ ↩⁶ ↩⁷ ↩⁸ ↩⁹ ↩¹⁰

27. 総務省消防庁 (FDMA). 「救急安心センター事業（♯7119）実施団体基本情報調査一覧」. https://www.fdma.go.jp/mission/enrichment/appropriate/appropriate010.html ↩ ↩² ↩³ ↩⁴

28. JNTO. "Japan Visitor Hotline". https://www.japan.travel/en/plan/hotline/ ↩

29. 大塚製薬工場 (Otsuka Pharmaceutical Factory). "OS-1 Oral Rehydration Solution Series" (English). https://www.os-1.jp/en/ ↩ ↩² ↩³ ↩⁴

30. 環境省熱中症予防情報サイト. 「熱中症の予防方法と対処方法」. https://www.wbgt.env.go.jp/doc_prevention.php ↩ ↩²

31. 総務省消防庁 (Fire and Disaster Management Agency). 「令和７年（５月～９月）の熱中症による救急搬送状況」 (annual report PDF, 2025-10-29). https://www.fdma.go.jp/disaster/heatstroke/items/r7/heatstroke_nenpou_r7.pdf ↩

32. 熱中症ゼロへ (Netsuzero, Japan Weather Association). "2025年の熱中症にまつわるニュース" (2025-11-20). https://www.netsuzero.jp/news/news-zero/20251120-14915.html ↩ ↩²

33. Nippon.com. "Weekly Emergency Heatstroke Cases Rise Above 10,000 in Japan" (2026-07). https://www.nippon.com/en/japan-data/h02849/ ↩ ↩²

34. 国立環境研究所 気候変動適応情報プラットフォーム (A-PLAT, NIES). 「記録的猛暑の時代を生き抜く！熱中症から身を守る"暑熱順化"のすすめ」. https://adaptation-platform.nies.go.jp/climate_change_adapt/heatstroke/column/hs-01.html ↩ ↩² ↩³ ↩⁴