A total of 6,165 people were taken to hospitals across Japan with symptoms of heatstroke or heat exhaustion in the week through Sunday, almost double the figure from a week earlier, government data showed Wednesday.
Of the total, 14 died on the way to the hospital, 178 required hospitalization for more than three weeks and 2,200 were hospitalized briefly, the Fire and Disaster Management Agency said in a preliminary report.
About half were aged 65 or older.
By prefectures, Saitama topped the list with 605 hospital admissions, followed by 578 in Tokyo and 340 in Osaka. Six people died in Saitama, followed by three in Iwate and one each in Fukushima, Tochigi, Gunma, Tokyo and Hyogo.
In the month from May 19 a total of 14,401 people were taken to hospitals as a result of the heat, up from 12,347 for the same period last year.
The agency warned that the hot weather was likely to continue, with the rainy season now officially finished in most areas of Japan.
Last week, a Fire and Disaster Management Agency official said, "Our bodies are not used to high temperatures at this time of the year, so we should drink water often even if we are not thirsty (to avoid dehydration)."