Temperatures soared in eastern and western Japan on Saturday, with daytime highs topping 39 degrees Celsius in some areas.
The Meteorological Agency says a high pressure system as well as hot and dry foehn winds pushed up temperatures.
Daytime highs reached 39.6 degrees in Tatebayashi City in Gunma Prefecture and Shimanto City in Kochi Prefecture, and 39.2 degrees in Mino City in Gifu Prefecture.
The mercury also hit 39 degrees in Kumagaya City in Saitama Prefecture, Hamamatsu City in Shizuoka Prefecture and Nagoya City.
Daytime highs reached 35 degrees or above in 212 locations across the country.
Weather officials are warning of another scorching day on Sunday with temperatures reaching 38 degrees in the cities of Nagoya and Gifu as well as Totsukawa Village, Nara Prefecture.
Daytime highs are expected to hit 37 degrees in Sumoto City in Hyogo Prefecture, and Yamaguchi City, 36 degrees in the cities of Osaka, Hiroshima, Takamatsu and Kumamoto, and 35 degrees in the cities of Kobe, Fukuoka and Matsuyama.
The Meteorological Agency and the Environment Ministry have issued heatstroke alerts for 28 of Japan’s 47 prefectures, between the Kanto-Koshin and Kyushu regions.
Many people have been taken to hospital this summer with suspected symptoms of heatstroke. Fatalities have been reported.
Officials are calling on people to refrain from outings and exercise, use air conditioners and consume water and salt.
They also urge people to pay close attention to senior citizens, babies and younger children, as they are especially vulnerable to extreme heat. People planning outdoor leisure activities are advised to carry ice in water bottles and ice packs.