Japan in summer: how to survive the heat

I’ve been living in Japan for over fifteen years and summer is still the hardest part of each year. Not because of the heat alone, which you’ll find worse elsewhere in the world, but because of the combination of temperature and humidity. In August in Tokyo or Osaka the feels-like temperature regularly exceeds 40°C. People walk around with handheld fans and ice towels. Trains are air-conditioned to maximum. And the Meteorological Agency issues heatstroke alerts with a regularity that takes some getting used to.

2026 is shaping up as one of the hottest summers on record in Japan. If you’re travelling here or living here, this is what you need to know — pair it with our broader guide to visiting Japan in summer if you’re still planning the trip.

---

Why Japan’s summer heat is different

The problem isn’t just the temperature. It’s the humidity.

Japan has a monsoon summer: after the rainy season (tsuyu, 梅雨) ends in July, the air is saturated with moisture. Relative humidity between 70% and 90% is normal in July and August in the major Pacific coast cities. At 35°C with 85% humidity, the body can’t dissipate heat efficiently. Sweat doesn’t evaporate. The real feel can be 42-44°C.

The urban heat island effect in Tokyo, Osaka and Nagoya amplifies this further: asphalt, buildings and the residual heat from air conditioning units keep temperatures high overnight, preventing the body from recovering.

---

Japan’s official alert system (熱中症警戒アラート)

Japan has an official heatstroke alert system (netchūshō keikai alert, 熱中症警戒アラート) based on the WBGT index (Wet Bulb Globe Temperature). This index combines temperature, humidity and solar radiation to measure actual heatstroke risk.

The levels are:

• Caution (注意): WBGT 25-28°C
• Warning (警戒): WBGT 28-31°C
• High warning (厳重警戒): WBGT 31-33°C
• Danger (危険): WBGT ≥33°C → at this level, authorities recommend avoiding outdoor activity during the central hours of the day

In summer 2026, the “danger” level has been triggered repeatedly in the densest parts of the Kanto and Kansai regions. The WBGT map is available on the Japan Meteorological Agency website (jma.go.jp) and in several weather apps.

---

What to buy at the convenience store

The konbini (convenience store) is your main ally against the Japanese heat. They’re always air-conditioned to the maximum, which means going in to buy something also doubles as a legitimate excuse to escape the heat. Inside you’ll find the most useful items:

Drinks:

• Pocari Sweat (ポカリスエット): the benchmark for electrolyte rehydration. It’s not water with sugar: it’s formulated to replace what you lose when sweating. One 500 ml bottle per day on intense heat days is a sensible baseline.
• Aquarius (アクエリアス): similar, slightly milder in taste. Both are in every convenience store.
• Salted drinks: drinks with added sodium, very useful for replacing the salt lost through sweat.

Plain water alone is not enough on intense heat days with a lot of movement. If you only drink water and sweat heavily, you can develop hyponatraemia (low sodium) which in serious cases causes dizziness and confusion.

Cooling items:

• Ice towels (hiyashi towel, ひんやりタオル): dampened, waved in the air, and cooled by evaporation. Effective for cooling the neck and wrists.
• Handheld electric fan (handy fan, ハンディファン): from 100-yen shops or Amazon Japan. Essential for commutes.
• Cooling body spray (cool spray): an aerosol that creates a cooling sensation on the skin. Useful for long metro journeys or temple visits with no shade.

---

What to wear

• Light colours: reflect more solar radiation than dark ones.
• Linen or light cotton: or technical fabrics with ventilation. Synthetic fabrics that don’t breathe worsen the heat feel.
• Parasol (higasa, 日傘): one of Japan’s smartest habits. A good parasol reduces direct sun exposure and lowers the feels-like temperature by several degrees. Men use them in Japan too, with no social stigma whatsoever.
• Light long sleeves: counterintuitively, a very thin long-sleeved technical fabric top can protect better from the sun than a sleeveless shirt, reducing the heat load on exposed skin.
• High SPF sunscreen: Japan’s market has some of the most effective sunscreens in the world. SPF 50+ PA++++ with sweat resistance is the sensible minimum for outdoor visits.

---

When to go out (and when not to)

The most dangerous hours are between 10:00 and 16:00, with the peak from 13:00 to 15:00. During those hours:

• Direct solar radiation is at its highest
• Asphalt accumulates and re-emits heat
• Heatstroke risk multiplies

Practical strategy:

• Outdoor visits: before 9:30 or after 17:00
• Central hours: museums, air-conditioned shopping centres, restaurants, time at the hotel
• If you have to be outside during peak heat hours: look for consistent shade, pause every 45-60 minutes in a cooled space, and always carry water or an isotonic drink

---

Recognising and treating heatstroke

Heatstroke (netchūshō, 熱中症) in Japan is a routine medical emergency in summer. It causes thousands of hospitalisations every year.

Mild symptoms (heat exhaustion):

• Heavy sweating
• Weakness, dizziness when standing
• Pale and damp skin
• Headache, nausea

Severe symptoms (heatstroke proper):

• Body temperature >40°C
• Cessation of sweating (skin feels dry and hot)
• Confusion, erratic behaviour
• Loss of consciousness

What to do:

• Move the person to a cool place immediately
• Lay them down with legs elevated
• Cool the body: damp towels on the neck, armpits and wrists
• If they can swallow: fluids with electrolytes
• If there is confusion, loss of consciousness or very high temperature: call 119 (emergency services in Japan)

In any Japanese drugstore or large convenience store you can find salt tablets (shio tablet, 塩タブレット) specifically for replacing minerals. They’re cheap and worth keeping in a bag.

---

At temples and shrines

Most major temples and shrines have no air conditioning and minimal shade between buildings. The white gravel surrounding many Shinto shrines and garden complexes amplifies solar reflection considerably.

Specific advice:

• Wear a hat or visor. Direct sunlight on the head is the most immediate risk factor
• Aim for outdoor temple visits before 9:00 where possible
• Many temples have vending machine areas inside. Use them
• Fushimi Inari in Kyoto has considerable shade in the upper sections (the cedars make a real difference) but the first 30 minutes of the ascent are in full sun

---

Air conditioning in Japan: practical notes

Indoors in Japan in summer can be the opposite extreme: trains, shops and some restaurants run their air conditioning at temperatures that feel cold. It’s common to see Japanese people with a thin jacket in their bag for interiors.

Japanese hotels typically have individual room temperature control. The integrated air conditioning and heating unit is standard even in mid-range hotels. Don’t set it to an extreme low all night: the temperature difference between inside and outside when you step out in the morning makes the heat feel worse.

---

FAQ

Which months are the worst? July and August. June has the rainy season, which keeps temperatures lower but with high humidity — it’s also hydrangea season, so the trade-off has its own reward. September improves, though the first days can still be hot and it’s typhoon season.

Is Hokkaido a good alternative for summer? Yes. Sapporo and the interior of Hokkaido are notably cooler than Honshu in summer, one of the island’s main draws in July and August. Though in 2026 even Hokkaido has seen abnormal temperatures.

Is it worth visiting Japan in summer if I don’t handle heat well? With planning, yes. Museums, covered markets, shaded shrines, restaurants and underground city networks (like those in Tokyo and Osaka) allow a full visit with minimal sun exposure — and a proper onsen with outdoor pools is a better way to cool down than it sounds. The main problem arises when you try to spend ten hours moving around in outdoor spaces.

Do Japanese people suffer from the heat too? Yes, though they’re more acclimatised. Japanese summer news regularly covers the number of people hospitalised for heatstroke each week. It’s not tourist hyperbole.

---

The 2026 temperatures and alerts are among the highest recorded in recent years across several Japanese cities. Check the Japan Meteorological Agency (jma.go.jp) for real-time alerts before any outdoor day out.