Tokyo, Aug 19 (IANS): Japan's weather agency on Monday said rain clouds are developing across Japan, with the Shikoku and Kyushu regions expected to see torrential thundershowers due to very unstable atmospheric conditions.

According to the Japan Meteorological Agency (JMA), a cold air mass is flowing into western and eastern Japan at high altitudes, while moist air from a tropical storm formed on Monday is flowing into areas around western Japan.

Rainfall of 30.5 millimetres was recorded during the hour through 5 a.m. local time in the city of Miyazaki and 30 millimetres in a district of the town of Shimanto in Kochi Prefecture, reports Xinhua news agency, quoting JMA.

The agency warned of flooding in low-lying areas, landslides and the sudden swelling of rivers, adding lightning strikes, hail and gusty winds including tornadoes are also possible.

Meanwhile, intense heat in Japan has been continuing on Monday, with heatstroke alerts issued for 19 of the country's 47 prefectures, according to the JMA.

Weather officials said temperatures are forecast to reach 36 degrees Celsius in the city of Matsue in Shimane Prefecture and the city of Kofu in Yamanashi Prefecture, as well as the cities of Nagoya and Yamagata.