Japan’s First “Kokushobi”: Temperatures Surge Above 40 °C

Mon Sep 14 2026 09:03:39 GMT+0000 (Coordinated Universal Time)

Japan experiences its first cruelly hot day, with temperatures surpassing 40°C in central cities, prompting urgent heatstroke warnings.

Japan has recorded its first "kokushobi", a newly coined term for days with temperatures above 40 °C. The heat swept through three central cities—Tajimi, Gujo and Toyoda—setting the stage for a prolonged hotter season. Meteorological agencies have issued heat‑stroke alerts across more than 40 prefectures, urging the public to stay hydrated and avoid outdoor exertion. The city of Tokyo has seen a record‑high number of heat‑stroke hospital visits, and officials are encouraging workers to adopt lighter clothing. This event underscores the growing intensity of global heatwaves amid climate change concerns.

Japan’s First “Kokushobi”: Temperatures Surge Above 40 °C

By Koh Ewe

3 hours ago

Japanese school girl with umbrellas on a summer day

Japan’s weather agency has used the newly coined term “kokushobi”, meaning “cruelly hot day”, to describe temperatures over 40 °C (104 °F). On Tuesday, three central cities—Tajimi, Gujo and Toyoda—reached this threshold, sparking a nationwide warning.

The Japan Meteorological Agency (JMA) predicts that the heat will persist into next week, with nearly 300 of the country’s 914 observation points recording a so‑called moshobi (extremely hot day) during the same period.

Last year, Japan recorded its highest ever temperature of 41.8 °C (107.24 °F) in Isesaki, and this recent heat wave raises concerns over the growing frequency and severity of extreme weather events worldwide.

With over 40 prefectures issuing heat‑stroke alerts, authorities advise citizens to use air‑conditioners, drink plenty of water, replenish electrolytes, and avoid prolonged outdoor activity.

The Tokyo Fire Department reported that 287 people, ranging in age from three to 103, were taken to hospitals on Tuesday due to heatstroke— the highest figure recorded this year. The department also issued an ambulance‑overload alert the following day.

Heatstroke incidents among workers peaked last year at 1,803, with 19 fatalities, underscoring the physiological risks of succumbing to the harsh heat. In response, the Tokyo government has urged office workers to wear more casual attire—such as T‑shirts and shorts—to better cope with the rising temperatures.