The Meteorological Agency on Monday warned of heavy rain, strong winds and rough seas as Typhoon Lionrock swirled off Japan's eastern coast.
The storm was forecast to strike eastern or northern Honshu, possibly including the Tokyo region, early Tuesday.
As of 9 p.m. Monday, the typhoon was moving over the Pacific Ocean about 350 km east of Hachijo Island in the Izu chain at a speed of around 25 kph, the Meteorological Agency said.
It was packing winds of up to 198 kph with an atmospheric pressure of 960 hectopascals near its center.
The season's 10th typhoon was expected to gain strength before making landfall in the Tohoku region, the agency said.
All Nippon Airways and Japan Airlines said they will cancel a total of 50 flights departing from and arriving at airports in the Tohoku region and Hokkaido on Tuesday. Many schools in Tohoku will cancel classes for the day.
Tohoku could see up to 500 mm of rain over the 24 hours to noon Wednesday, more than the entire monthly average for August, the weather agency said.
Officials added that landslides are possible, triggered by heavy rain.
While winds of up to 180 kph were projected for Tohoku, gusts of 126 kph were expected in Hokkaido and Kanto on Tuesday.
Hokkaido and Kanto could see up to 150 mm of rain by Tuesday morning, it said.