Areas in the northern Kyushu and Kanto Koshin regions were hit by torrential rain caused by extremely unstable atmospheric conditions late Wednesday.

Weather officials are warning of possible sporadic downpours overnight as warm and damp air continues to flow into the regions.

Radar analysis has found that an area in Hokuto City, Yamanashi Prefecture, was hit by about 100 millimeters of rain in the hour through 9:30 p.m., as well as over 120 millimeters an hour several hours earlier.

Radar analyses showed that areas near the cities of Yame and Kurume in Fukuoka Prefecture, southwestern Japan, were likely pounded with downpours of over 120 millimeters in the hour through 10 p.m.

Rain of 142 millimeters was registered in Yame City during the same time frame. This means the city recorded 60 percent of rainfall for the month of August in just an hour.

As rainclouds moved south, Yamaga City in Kumamoto Prefecture saw rain of 81 millimeters in the hour through 11 p.m.

Weather officials are warning of flooding in low-lying areas, swollen rivers and mudslides as well as lightning and tornadoes.