The Tokai region recorded Japan’s first domestic “酷暑日,” or extremely hot day, on July 21, 2026, as temperatures reached 40°C and above [1].
This milestone marks the beginning of a critical period for public health and infrastructure. The Japan Meteorological Agency (JMA) has issued high-temperature advisories and warnings for heat-related illness as the nation grapples with a persistent heat wave [1, 4].
In Gifu Prefecture, temperatures reached 40°C in Gujo Hachiman before 2 p.m. [1]. Later in the day, Tajimi City in the same prefecture recorded a peak of 40.3°C [1]. Aichi Prefecture also saw extreme readings, with Toyota City reaching 40.1°C [1].
The heat extends beyond the Tokai region. In Ibaraki Prefecture, Koga City recorded a maximum temperature of 39.6°C [1]. Central Tokyo also experienced significant heat, reaching 36.4°C [1].
Nationwide, the scale of the heat wave is evident in the data. Approximately 30% of all monitoring sites, totaling 278 locations, recorded extreme-heat days with temperatures exceeding 35°C [1].
This event continues a worrying trend of rising summer temperatures. According to the JMA, this is the ninth consecutive year that at least one location in Japan has recorded a temperature of 40°C [1].
“The Tokai region recorded Japan’s first domestic “酷暑日” as temperatures hit 40°C-plus.”
The consistent occurrence of 40°C temperatures for nearly a decade indicates that extreme heat is becoming a systemic seasonal norm rather than an anomaly in Japan. The widespread nature of this heat wave—affecting nearly a third of the country's monitoring stations—suggests an increasing strain on urban cooling infrastructure and a heightened risk of heatstroke across diverse geographic regions.
