Japanese weather officials warn that a tropical depression south of Okinawa will strengthen as it heads north. They say it could reach eastern Japan on Friday.
The Japan Meteorological Agency says the depression is expected to move toward Okinawa's main island on Wednesday night, and then north along the Amami Islands.
The agency says the depression could approach the Pacific coast of western Japan on Thursday and reach eastern Japan on Friday.
Landslide warnings have been issued for parts of Okinawa's main island as torrential rain continues.
A rain front is expected to move north with the depression, making atmospheric conditions unstable across wide areas. Weather officials warn of localized heavy rainfall exceeding 50 millimeters an hour.
As much as 300 millimeters of rain is expected in the Shikoku region and 250 millimeters in southern Kyushu in the 24-hour period through Thursday evening.
The Meteorological Agency is calling for extreme caution against landslides and floods in low-lying areas.