A seasonal rain front and a low pressure system have been causing unstable atmospheric conditions and bringing heavy rain mainly to Kyushu, southwestern Japan.
Weather officials are warning that landslides may occur, as the soil has already been saturated by rain that fell up to Friday.
Japan’s Meteorological Agency says warm moist air flowing into the rain front and a low pressure system over the Kyushu and Tokai regions are making the atmospheric conditions in western and eastern Japan extremely unstable.
The Kyushu, Shikoku, and Tokai regions have been intermittently covered by rain clouds.
Rainfall levels from 5 a.m. to 6 a.m. on Friday were as follows: 39 millimeters in the city of Unzen in Nagasaki Prefecture; 34 millimeters in the town of Suo-Oshima in Yamaguchi Prefecture; and 30 millimeters in the city of Kosai in Shizuoka Prefecture.
Ibusuki City and Kinko Town in Kagoshima Prefecture have received more than 700 millimeters of rain since June 20. That is more than they would normally receive for the whole month of June during an average year.
Parts of Kagoshima Prefecture are under a mudslide alert.
A seasonal rain front will bring extremely heavy rain to western and eastern Japan on Friday, and heavy rain on Saturday.
Expected rainfall levels for the 24-hour period through Saturday morning are as follows: up to 200 millimeters in the Tokai and Kinki regions, 180 millimeters in southern Kyushu, 150 millimeters in Shikoku and northern Kyushu, and 100 millimeters in Hokuriku.
The agency is warning there is a chance that the risk of disaster could rise suddenly, as the bands of rain clouds that are expected to be generated on Friday morning in Fukuoka, Oita and Kumamoto Prefectures will bring persistent heavy rain.
Caution is advised against mudslides, flooding in low-lying areas, and swollen or overflowing rivers. Weather officials are also warning that lightning strikes and gusty winds could occur.
The authorities say that people should pay close attention to evacuation information provided by their municipalities and stay in a safe place for the time being, as weather conditions can deteriorate quickly.