Japan creates “kokushobi” for extreme heatwaves

With temperatures now climbing above 40°C, Japan has coined an entirely new word to describe its most extreme heatwaves. This unprecedented move highlights the harsh impact that global overheating is having on everyday life.

Extreme heatwaves across the Northern Hemisphere

Summer 2026 has been defined by periods of intense heat, not only in France but throughout the Northern Hemisphere. Climate change partly explains this pattern: year after year, heatwaves are reshaping what is considered normal worldwide.

El Niño intensifies global weather patterns

This year, global weather events are also being intensified by El Niño, a recurring oceanic disruption marked by unusually warm Pacific waters. It has a direct effect on global temperatures and is far more intense than in 2023, the last time it occurred.

As widespread overheating takes hold, governments are being compelled to rethink their prevention measures. Against this backdrop, Japan has taken the symbolic step of adapting its vocabulary itself.

Japan coins the term “kokushobi”

To warn the public, the Japan Meteorological Agency has formally introduced a new expression: kokushobi, which can be translated as “a cruelly hot day”. The term now applies to peaks above 40°C, extending an existing scale that already describes days exceeding 25°C (natsubi), 30°C (manatsubi) and 35°C (moshobi).

On Tuesday 21 July, several cities in the centre of the country crossed this symbolic threshold. In Tokyo alone, hundreds of people were admitted to hospital with heatstroke in a single day, almost overwhelming emergency services, while Japan has already recorded more than 2,000 heat-related deaths during recent seasons.

Japanese society adapts to extreme heat

Everyday life in Japan is being reorganised around extreme temperatures. For instance, authorities are now encouraging employees to wear shorts and T-shirts in the office. The change is intended to cut air-conditioning use and ease pressure on an already strained electricity network.

Similarly, the iconic national high-school baseball tournament, held in the height of August, will split its fixtures between the morning and evening to safeguard players and spectators. Rice growers are turning to more heat-resistant varieties, while others are converting their land to avocado cultivation.