Japan is grappling with an unprecedented heatwave, with heatstroke alerts issued across multiple regions. This period, typically marked by the rainy season, has instead seen an early onset of extreme heat due to climate change, significantly impacting both tourists and residents. On June 18, Tokyo recorded a high of 34.4°C (93.9°F), leading to a surge in emergency medical visits, with research suggesting over 562 people transported to hospitals in Tokyo this month alone for heatstroke.
Weather Conditions
The heatwave began intensifying around June 17, with temperatures soaring well above seasonal averages. Research indicates that on June 17, Kofu in Yamanashi Prefecture reached 38.2°C (100.8°F), Takasaki in Gunma Prefecture hit 37.7°C (99.9°F), Shizuoka in Shizuoka Prefecture recorded 37.6°C (99.7°F), Sendai in Miyagi Prefecture saw 34.7°C (94.5°F), and Osaka in Osaka Prefecture noted 33.4°C (92.1°F). These readings were significantly higher than expected, with Kofu’s 38.2°C being particularly anomalous.
On June 18, Tokyo hit 34.4°C (93.9°F), and central regions experienced even higher temperatures. The Japan Meteorological Agency reported that 14 cities set new June temperature records, and the Kanto region saw “extremely hot days” with temperatures above 35°C (95°F). The evidence leans toward high temperatures persisting until at least June 20, with forecasts indicating Kyoto and Nara reaching 36°C (96.8°F), and Gifu and Nagoya potentially hitting 37°C (98.6°F). For the latest updates, check the Japan Meteorological Agency.
Below is a table summarizing the temperature data:
| City | June 17 High (°C) | June 18 Forecast (°C) |
| Kofu | 38.2 | – |
| Takasaki | 37.7 | – |
| Shizuoka | 37.6 | – |
| Sendai | 34.7 | – |
| Osaka | 33.4 | – |
| Tokyo | – | 34.4 |
| Kyoto | – | 36 |
| Nara | – | 36 |
| Gifu | – | 37 |
| Nagoya | – | 37 |
Impact and Casualties
The heatwave has had severe consequences, with research suggesting four elderly women died from heatstroke on June 17 in Kanagawa, Shizuoka, Saitama, and Gunma prefectures, highlighting the heightened risk for older individuals. In Tokyo, 169 people sought emergency care for heatstroke on June 17, followed by 57 more on June 18. Nationwide, from May to June 8, 3,833 individuals were hospitalized for heatstroke, with numbers continuing to rise. The Tokyo Fire Department reports that over 562 people have been transported to hospitals for heatstroke this month alone, underscoring the widespread health impact, particularly on the elderly and those with pre-existing conditions.
Alerted Regions
Heatstroke alerts have been issued in the following prefectures: Ibaraki, Chiba, Wakayama, Kagoshima, Kagawa, Miyazaki, and Okinawa. These areas are under special watch by the Japan Meteorological Agency, with strong recommendations for residents and tourists to take preventive measures. For detailed regional alerts, visit the Fire and Disaster Management Agency.
Impact on Tourists
From January to May 2025, Japan welcomed a record 18.14 million foreign tourists, increasing the risk of heatstroke, especially in crowded destinations like Tokyo, Kyoto, and Nara. The combination of high temperatures and tourist congestion heightens the danger, making precautions essential. Tourists are advised to drink water frequently (every 10-20 minutes), rest in shaded or air-conditioned areas, and avoid outdoor activities between 10 AM and 4 PM. The Fire and Disaster Management Agency also recommends using air conditioning, cooling the neck and armpits, and dressing lightly to mitigate risks.
Japan Meteorological Agency’s Warnings
The Japan Meteorological Agency has warned that high temperatures may continue through June 20, urging particular caution for the elderly, those with health issues, tourists, and outdoor workers. Recommended actions include frequent hydration and use of air conditioning, with the latest updates available on their website (Japan Meteorological Agency).
Background and Additional Notes
The 2025 summer is particularly vulnerable to climate change and extreme heatwaves, with last year’s summer marking one of the hottest on record. Japanese authorities are actively promoting heatstroke prevention for tourists through official websites and apps, ensuring travelers have access to critical safety information.
Information Sources
For the latest updates, check:
Key Citations
- Japan on alert after four people die amid early summer heatwave
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- Japan Issues Alert Amid Deadly Early Summer Heatwave
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