Heatwave pushes Japan’s central region past 40°C, triggers new record

A persistent heatwave broke new ground in Japan on Tuesday, July 21, when three central cities each recorded temperatures exceeding 40 °C – the first official “Kokushobi” day recorded by the Japan Meteorological Agency.

The city of Tajimi in Gifu Prefecture topped the chart at 40.3 °C, while Gujō logged 40.0 °C and Toyoda in Aichi posted 40.1 °C. These figures meet the JMA’s Kokushobi threshold, a designation created in April to flag days of extreme heat and prompt stronger public safety messages.

The agency also noted that 731 out of 914 weather stations reported temperatures of 30 °C or higher, and 272 stations were categorized as “Mosho” – an “extremely hot day” label that does not yet encompass the newer Kokushobi classification.

Meteorologists traced the spike to a robust high‑pressure ridge that has been dominating the region since early Sunday, amplifying heat at both ground level and in the upper atmosphere. Authorities warned that similar conditions could continue into the coming days, advising citizens to stay cool, remain hydrated, and monitor for symptoms of heat‑related illnesses.