Northern Japan was braced for torrential rain, high waves and powerful gusts of wind on Thursday as Typhoon Dianmu barrelled towards the archipelago after leaving five people dead in South Korea.
Dianmu, packing winds of more than 80 kilometres (50 miles) per hour near its centre, was churning northeast in the Sea of Japan at midday, the country's weather agency said.
It was on course to make landfall in northern Japan late on Thursday.
The storm's arrival coincides with Japan's mid-August holiday break. The agency warned heavy rain could trigger flooding of rivers and mudslides while waves could be as tall as five metres (16 feet)
Rainfall could reach 20 centimetres (eight inches) in northeastern Japan in the 24 hours to midday on Friday, according to the agency.
Torrential rain brought by the approach of Dianmu left five people dead and grounded dozens of flights in South Korea.
The typhoon made landfall on the south coast of the Korean Peninsula early on Wednesday and dumped more rain as it passed through the country towards Japan.