Japan recorded its first official ‘cruelly hot day’ (kokushobi) on Tuesday, when temperatures topped 40°C in central cities like Gujo, Tajimi, and Toyota. This new designation warns of formerly freak events now becoming common due to climate change. The Japan Meteorological Agency introduced the term in April to highlight extreme heat dangers.
What is a ‘Cruelly Hot Day’?
The new category applies to days exceeding 40°C, a threshold rarely seen in Japan until recent years. Previously, the highest warning was moshobi (extremely hot days) for temperatures over 35°C. Lower categories include natsubi (summer days) above 25°C and manatsubi (true summer days) above 30°C.
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| Category | Temperature Range | Japanese Name |
|---|---|---|
| Summer Day | 25°C+ | Natsubi |
| True Summer Day | 30°C+ | Manatsubi |
| Extremely Hot Day | 35°C+ | Moshobi |
| Cruelly Hot Day | 40°C+ | Kokushobi |
Deadly Consequences of Extreme Heat
On Monday, a man in his 40s was found dead on a street in Sanjo, Niigata prefecture, and another in his 70s died in Kanagawa, southwest of Tokyo. Both are believed to have succumbed to heatstroke. In 2024, heatstroke deaths topped 2,000 for the first time, with over 100,000 hospitalizations from May to September, according to the fire and disaster management agency.
Impacts on Agriculture and Sports
The rising heat is affecting rice yields, a staple crop. Farmers are planting heat-tolerant rice varieties and switching to avocadoes. In sports, the popular Koshien national high school baseball tournament restructured game times into morning and evening sessions since 2024 to reduce heatstroke risk for players and spectators. Office workers are also encouraged to wear shorts on hot summer days.
Key Takeaways
- Japan’s first ‘cruelly hot day’ (40°C+) recorded in Gifu and Aichi prefectures.
- Heatstroke deaths exceeded 2,000 in 2024; over 100,000 hospitalized.
- Farmers adapt with heat-tolerant crops; sports events rescheduled.
- New temperature warnings aim to improve public safety.
FAQ
What is a 'cruelly hot day' in Japan?
It is a new official warning for days when temperatures exceed 40°C, coined by the Japan Meteorological Agency in April 2025 to highlight the danger of extreme heat.
How many people died from heatstroke in Japan in 2024?
Heatstroke fatalities surpassed 2,000 for the first time in 2024, with over 100,000 emergency hospitalizations during the summer months.
What are the temperature categories used by Japan's weather agency?
Categories include natsubi (summer days, 25°C+), manatsubi (true summer days, 30°C+), moshobi (extremely hot days, 35°C+), and kokushobi (cruelly hot days, 40°C+).
How is Japan adapting to rising temperatures?
Farmers plant heat-tolerant rice and switch to crops like avocado. The Koshien baseball tournament now schedules morning and evening sessions, and offices allow shorts to reduce heatstroke risk.
Stay safe during extreme heat: drink water, avoid direct sun, and check on elderly neighbors. For more updates on heatwave risks and health tips, explore our other guides.
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