The Tokyo Fire Department said 453 people were taken to hospital on Wednesday due to heat-related conditions.
Tokyo recorded its highest number of daily heat-related hospitalisations since 2010 on Wednesday, as Japan continued to battle a severe heatwave. Emergency services reported one death, while four people were in critical condition.
The Tokyo Fire Department said 453 people were taken to hospital on Wednesday, marking the highest daily figure since heat-related records began in 2010.
The number of emergency service deployments recorded that day also reached the highest level in 63 years.
“We are urging people to stay hydrated and use air conditioners,” a fire brigade spokesman told AFP on Thursday.
The spokesman said the number of heat-related patients appeared to increase as temperatures climbed, with a particularly noticeable rise on Wednesday and the previous day.
He said one person had died, while four others were in critical condition and 18 were in a serious state in Tokyo prefecture, which is home to around 14 million people.
In central Aichi prefecture, which includes the city of Nagoya, 116 people were taken to hospital on Wednesday due to heat-related conditions, officials said.
The same day, four locations — one in Mie, two in Gifu and one in Shizuoka — recorded temperatures above 40°C, according to the Japan Meteorological Agency (JMA).
Japan introduced a new term this year for extreme heat above 40°C: “kokushobi”, which translates to “cruelly hot day”.
The new term was introduced to raise public awareness about the dangers of extreme heat, although it does not activate any official nationwide measures.
At least six other locations recorded temperatures of 39.8°C on Wednesday.
Heatstroke alerts were issued across almost the entire country, with emergency officials saying at least 14 people had died from heat-related causes over the past week.
According to Japan’s Fire and Disaster Management Agency, nearly 11,000 people sought emergency medical care for heat-related conditions during the same period.
Fourteen of those victims were pronounced dead on arrival, the agency said, warning that the public should treat the extreme heat as a “disaster”.
“Temperatures have been rising since mid-July, and severe heat is expected to continue nationwide,” Japan’s disaster agency said.
“It is no exaggeration to call this extreme heat a ‘disaster’, with many people being taken to hospital or even losing their lives due to heatstroke,” it added.
Scientists say human-driven climate change is contributing to more frequent and intense extreme heat events in Japan and around the world.
Japan experienced its hottest summer on record last year.
The country’s highest-ever recorded temperature was measured on August 5, 2025, when Isesaki, north of Tokyo, reached 41.8°C.
