Eastern and western Japan were gripped by sweltering heat on Thursday as hot weather continued.

The day's hottest temperature -- 39.1 degrees Celcius --- was recorded in the town of Aki Ohta in Hiroshima Prefecture in western Japan. It's the first time ever that the prefecture has logged temperatures topping 39.

The Meteorological Agency said a high pressure system brought clear skies to much of Japan, from Tohoku in the north, down to Okinawa in the south.

Toyonaka City in Osaka had a daytime high of 38.7; Kyoto City, 38.3; and Osaka City, 37.3.

The heatwave is expected to continue on Friday. The mercury is forecast to hit 39 in Kyoto City, and 38 in Nagoya, Nara, and several other cities in western Japan. Yokohama City near Tokyo can expect a daytime high of 35.

The agency and the Environment Ministry have issued heatstroke alerts for Thursday to 32 of Japan's 47 prefectures, from the Kanto region in eastern Japan, down to the Kyushu region in the south.

People are strongly encouraged to use air-conditioners, and to take adequate amounts of fluid and salt to stay hydrated. Special attention should be paid to elderly people and young children because they are at higher risk of developing heatstroke.