Japan's Meteorological Agency says atmospheric conditions are unstable in western and eastern regions of the country.
Weather officials are urging people to be on alert for possible mudslides and sudden swelling of rivers, as they expect heavy downpours from western to northern Japan through Saturday.

The agency says warm and humid air has been flowing into a low-pressure system moving eastward over the Sea of Japan.

Kisarazu City in Chiba Prefecture saw 31.5 millimeters of rain, and Mihama Town in Fukui Prefecture 30.5 millimeters in the hour through 4:30 p.m. on Thursday.

Hourly downpours of 50 millimeters or more, accompanied by thunder, are forecast for western and eastern Japan, as well as more than 30 millimeters of rain in northern Japan through Friday midnight.

Until Friday evening, Southern Kyushu is expected to have as much as 120 millimeters of rain. Northern Kyushu, Chugoku, Tokai, Kanto-Koshin and Tohoku region are expected to have 100 millimeters, while Kansai and Hokuriku regions are forecast to have 80 millimeters.

From Friday evening through Saturday evening, 200 to 300 millimeters of rain are forecast for southern and northern Kyushu, and 100 to 150 millimeters for Tokai, Tohoku and Hokkaido.
The Chugoku, Kansai, Hokuriku and Kanto-Koshin regions are expected to have 50 to 100 millimeters.

Heavy rainfall has loosened the ground in many parts of Japan.
The Meteorological Agency is calling on people to remain cautious of mudslides, floods in low-lying areas and rising rivers, lightning strikes, tornados and gusting winds.

Officials are urging people to prepare in advance, such as checking where to evacuate.