If you’re visiting Japan between June and September, be prepared: the heat and humidity can feel intense—even oppressive—for many first-time visitors. Some even compare walking outside to “stepping into a sauna with clothes on.” But why is Japan’s summer weather so hot and humid compared to other countries? Here’s an explanation tailored for foreign tourists, with practical tips and real-world examples.
☀️ 1. Japan’s Geographical Position: Surrounded by Moisture
Japan is an island nation surrounded by the Pacific Ocean, the Sea of Japan, and several other bodies of water. These seas contribute a large amount of moisture to the atmosphere. Warm ocean air easily flows into Japan, especially in summer, increasing humidity levels.
- Example: Even if the temperature is “only” 30°C (86°F), the humidity makes it feel like 38°C (100°F+). You’ll sweat just walking 100 meters.
🌧️ 2. The Rainy Season (梅雨 – Tsuyu)
From early June to mid-July, Japan experiences a rainy season called tsuyu. During this time, the air becomes extremely moist due to constant rainfall and cloud cover. But even after the rain stops, the humidity stays.
- Example: Imagine it rains in the morning and the sun comes out in the afternoon—the moisture from the ground evaporates, creating a “steam room” effect.
🏙️ 3. Urban Heat Island Effect
In major cities like Tokyo, Osaka, or Fukuoka, concrete buildings, roads, and infrastructure absorb heat during the day and slowly release it at night. This keeps temperatures high even after sunset and traps moisture in the air.
- Example: At 10 p.m. in central Tokyo, it might still be 29°C (84°F), with 80% humidity—making it difficult to sleep without air conditioning.
⛰️ 4. Limited Natural Ventilation in Some Areas
Japan is mountainous, and many cities are located in basins or valleys, like Kyoto. These geographical features trap warm, moist air and reduce natural airflow.
- Example: Kyoto is often ranked among Japan’s most uncomfortable summer cities—not because of higher temperatures, but due to lack of wind and stifling humidity.
🔄 5. Monsoon Climate
Japan’s climate is classified as humid subtropical (Köppen classification Cfa). During summer, southern winds from tropical regions bring warm, moisture-laden air to Japan, leading to muggy, uncomfortable conditions.
- Tip: Don’t expect a “dry summer” like in parts of California or Italy. Japan’s summer is closer to places like Singapore or Hong Kong—but even more unpredictable.
🥵 How It Feels to Tourists
Many foreign travelers are shocked by:
- Constant sweating even when standing still.
- The need to shower multiple times a day.
- Dizziness, headaches, or heat fatigue after walking just 20–30 minutes.
🧊 How to Survive Japan’s Humid Summer: Practical Tips
- Hydrate constantly. Buy cold drinks from vending machines or convenience stores often.
- Use cooling products. Try cooling wipes, sprays, and wearable fans sold at stores like Don Quijote or Daiso.
- Wear light, breathable clothing. Avoid black or tight-fitting clothes.
- Take breaks indoors. Visit cafes, department stores, or museums with air conditioning.
- Avoid outdoor travel in the early afternoon (12–3 p.m.)—the hottest time of the day.
🏥 Warning: Watch for Heatstroke (熱中症 – Netchūshō)
Every summer, thousands of people—locals and tourists alike—are hospitalized due to heatstroke. Symptoms include:
- Nausea
- Confusion
- Fainting
- No longer sweating (a serious sign)
If you feel ill, seek shade or air conditioning immediately and drink water with electrolytes. Call emergency services (119) if symptoms worsen.
🌟 In Conclusion
Japan’s summer isn’t just hot—it’s humid, intense, and potentially dangerous if you’re not prepared. But with the right knowledge and a few smart habits, you can enjoy the festivals, food, and fireworks that make summer in Japan unique and memorable.