Japan experienced an intense heatwave on July 22, with temperatures soaring above 40 degrees Celsius in several cities, prompting the government to issue heatstroke warnings and introduce a new classification for extreme heat days. The Japan Meteorological Agency designated the day as a “brutally hot day,” or “kokushobi,” a term recently adopted to mark when temperatures reach or exceed 40 degrees Celsius.

The cities of Kumagaya, located north of Tokyo, and Nagoya, in central Japan, were among the areas expected to face the highest temperatures. Authorities advised residents to take precautions by using air conditioning generously, staying well-hydrated, and minimizing outdoor activities during peak heat periods.

Japan has seen an increase in the severity and frequency of heatwaves in recent years. Last year, the country recorded its highest-ever temperature of 41.8 degrees Celsius. Even prior to the current heatwave, there were significant health impacts; from July 6 to 12, a total of 4,580 people were hospitalized with heat-related illnesses, including seven fatalities, according to data from the Fire and Disaster Management Agency.

The introduction of the “kokushobi” classification reflects the government’s recognition of the escalating threat posed by extreme temperatures, aiming to raise public awareness and encourage preventive measures. During the 2025 summer alone, over 100,000 people were admitted to hospitals for heatstroke, underscoring the ongoing public health challenge presented by rising temperatures in Japan.