Japan has introduced a new term to describe extremely hot days that reach 40°C or higher, following a record-breaking summer. The word “kokushobi” now defines these intense heatwave conditions.
The Japan Meteorological Agency officially adopted the term after a nationwide survey. The phrase translates to “cruelly hot” or “severely hot,” reflecting the growing intensity of extreme weather.
Why Japan Created a New Term
The need for a new classification emerged after Japan experienced its hottest summer on record in 2025. Temperatures rose far above normal levels, pushing authorities to better communicate the dangers of extreme heat.
In the survey, which gathered nearly 478,000 responses, “kokushobi” ranked as the most popular choice among several options. The term combines the Japanese word “koku,” meaning harsh or cruel, with “shobi,” referring to a hot day.
Record-Breaking Heat Across the Country
Japan’s summer temperatures reached unprecedented levels. The national average rose 2.36°C above normal, marking the highest since records began in 1898.
Several cities experienced prolonged heatwaves. Tokyo recorded 25 days above 35°C—far exceeding its typical average. Kyoto saw even more extreme conditions, with 52 such days.
The city of Isesaki reported a peak temperature of 41.8°C, setting a new national record. Overall, the number of extremely hot days surpassed previous highs, highlighting a worrying trend.
Climate Change Driving Extreme Weather
Scientists link the rise in heatwaves to broader climate change patterns. Human activities, especially the burning of fossil fuels, continue to increase global temperatures.
Extreme weather events—such as heatwaves, droughts, and floods—are becoming more frequent and intense worldwide. Japan’s new term reflects not just a linguistic change, but a growing need to adapt to these conditions.
What to Expect Next
The Japan Meteorological Agency has warned that above-average temperatures are likely to continue during the upcoming summer months.
As extreme heat becomes more common, terms like “kokushobi” may play a key role in raising awareness and encouraging safety measures among the public.
