The Japan Meteorological Agency introduced a term, ‘kokushobi’ for days with temperatures above 40 degC. This word is a combination of koku, which means harsh or cruel (or savage), and strong data-end=”149″ data-start=”133″>kokushobi,” to describe days when temperatures reach 40degC or higher.
Japan Expands its Heat Categories
Japan classifies heat days according to temperature. Day temperatures above 25degC can be classified as warm. Days over 30degC, however, are hot. And days above 35degC, are extremely hot. This new category shows how the climate is changing.
The record-breaking summer pushes change
A historic heatwave prompted the decision. The summer of 2025 was the hottest ever recorded in Japan, dating back to 1898. The average temperature in Japan was 2.36degC above normal.
Extreme heat hits cities hard
The number of extremely hot days in major cities has increased dramatically. Tokyo had 25 days with temperatures above 35degC – a much higher average than the usual 4.5 days. Kyoto experienced even worse conditions with 52 days over 35degC, compared to an average of 18.5 days.
The figures indicate a marked increase in heatwaves, both their frequency and intensity.
The Heat is on this Year
Japan Meteorological Agency warned temperatures will likely remain above normal in this summer. Forecasts from June to August show a high probability of extreme heat in the entire country.
The trend shows the impact of global warming, with rising temperatures leading to a greater frequency and severity of heat waves.
