Japan experienced its fifth consecutive day of temperatures exceeding 40 Celsius on Sunday, a phenomenon labeled as “cruelly hot day” or “kokushobi” by the Japan Meteorological Agency (JMA). This marks the longest streak of such intense heat since the new warning system was introduced in 2010.

The JMA began using the “kokushobi” designation earlier this year to raise public awareness about extreme heat conditions, particularly those surpassing 40 degrees Celsius. Although the term does not trigger formal nationwide measures, it serves as a heightened advisory to encourage vigilance against heat-related risks. On Sunday, six cities in central Japan, including areas within Aichi and Gifu prefectures, reported temperatures above this threshold.

The extreme heat has led to a surge in heat-related health emergencies. Between July 13 and 19, nearly 11,000 people sought emergency medical care due to heatstroke or related symptoms, according to Japan’s Fire and Disaster Management Agency. Among these cases, 14 patients were declared dead upon arrival at medical facilities during that period. Officials emphasized the need to treat the extreme heat as a serious public health hazard.

Tokyo, in particular, saw a sharp increase in heat-related hospitalizations, with 453 patients treated on Thursday alone—the highest daily number recorded since tracking began more than ten years ago. Japan typically records about 1,300 heat-related deaths each year and has set a goal to reduce that number by half by 2030.

Experts link the rise in such extreme heat events to human-driven climate change, which they say is causing more frequent and intense heatwaves across Japan and globally. The country experienced its hottest summer on record in 2025, with a peak temperature of 41.8 Celsius reached on August 5 in Isesaki, north of Tokyo. The recent heatwave underscores ongoing concerns about public safety and the strain on health systems as climate change continues to impact weather patterns.