TOKYO - (Precipitation as of 1:55 a.m. Thursday. Source:Japan Meteorological Agency)

Japan's weather agency on Wednesday warned of heavy rains over the next day across a wide stretch of the country from the west, particularly on the southwestern main island of Kyushu.

The Japan Meteorological Agency said early Thursday that so-called rainbands have formed in five prefectures on the island -- Fukuoka, Kumamoto, Nagasaki, Oita and Saga -- heightening the risk of landslides, flooding in low-lying areas and water overflowing riverbanks.

Heavy rain was observed Wednesday, mostly in western Japan, as a warm, damp air mass flowed into low-pressure systems and a seasonal rain front stalled over the country, according to the agency.

The Nagasaki Prefecture island of Tsushima, northwest of Kyushu, saw over 100 millimeters of rainfall during a three-hour period on Wednesday morning.

The low-pressure systems and rain front are expected to move eastward over the main island of Honshu through Thursday, potentially causing rain and thunderstorms. The agency also said people should watch out for high winds, including tornadoes.

Over a 24-hour period through 6 p.m. Thursday, the agency is expecting up to 150 mm of rain on the main island of Shikoku and in northern and southern Kyushu, 120 mm in the Kinki region centering on Osaka Prefecture, and 100 mm in the Kanto-Koshinetsu region including Tokyo. Rainfall during the period could exceed projections in areas where rainbands form.