Japan temperatures soar over 40C, marking first 'cruelly hot day'

What the report says

BBC World News reported that Japan recorded its first “kokushobi,” a newly designated category for days when temperatures reach 40C (104F) or above. The label, which can be translated as “cruelly hot day,” was introduced in April by Japan’s weather agency to strengthen public warnings about severe heat.

According to the BBC, the threshold was reached on Tuesday in three central Japanese cities: Tajimi, Gujo and Toyoda. Japan’s Meteorological Agency said the heat was expected to persist into the following week. The new term adds to existing Japanese weather descriptions for days above 25C, 30C and 35C; days over 35C are already known as “moshobi,” or extremely hot days.

The report said heatstroke alerts had been issued in more than 40 prefectures, with officials urging residents to use air conditioning, stay hydrated, take in salt and limit extended outdoor activity. Citing Japanese media, the BBC said nearly 300 of Japan’s 914 observation sites recorded temperatures above 35C on Tuesday. NHK reported that Tokyo’s fire department transported 287 people, aged three to 103, to hospitals that day for apparent heatstroke, the highest daily figure in the city so far this year.

The development underscores growing concern about dangerous summer heat in Japan. The BBC noted that the country recorded a national high of 41.8C last year in Isesaki, and cited Kyodo as reporting a record 1,803 workplace heatstroke cases in 2024, including 19 deaths. More broadly, scientists have found that climate change is making many heatwaves more frequent and intense globally.