Weather officials say extremely heavy rain will hit the island of Kyushu in southwestern Japan through Thursday. They may issue emergency warnings if downpours continue for several hours in the same places.
The officials are warning people in the region to stay on the alert for rain-triggered disasters and to evacuate ahead of time without waiting for emergency advisories to ensure their own safety.
The meteorological agency says rain clouds are developing as a seasonal rain front hovers over the region and warm, humid air flows in.
Rainfall in some parts of southern Kyushu has exceeded 900 millimeters since Friday.
The city of Kanoya in Kagoshima Prefecture had 50.5 millimeters of rain between 7:45 and 8:45 a.m. on Wednesday.
Weather officials have issued mudslide warnings in Kagoshima, Kumamoto and Miyazaki Prefectures.
The officials say the rain front will become more active until Thursday, with localized downpours of more than 80 millimeters per hour for Kyushu. They forecast that daily rainfall will be as much as the monthly average for July.
Southern Kyushu is expected to have up to 350 millimeters of rain in the 24 hours through Thursday morning.
The officials say the downpours will intensify.
Maximum rainfall from Thursday noon through Friday noon is expected to be 100 to 200 millimeters in southern Kyushu and Tokai.