Powerful Typhoon Chaba was expected to move slowly northwest to approach or strike the Amami Islands and western Japan between Sunday and Monday, the Meteorological Agency said.
The season's 16th typhoon was expected to come close to Kyushu or Shikoku on Sunday while engulfing Amami and other outlying islands south of Kagoshima Prefecture in a rainstorm zone, the agency said, adding that it could strike the regions Monday.
The agency warned of strong winds, heavy rain and high waves in those areas as well as the Shikoku and Tokai areas.
Chaba, which means "hibiscus" in Thai, was located about 270 km northeast of Okinawa Prefecture's Minamidaito Island as of 7 p.m. Saturday.
The typhoon had an atmospheric pressure of 935 hectopascals and was packing winds of up to 162 km per hour near its center.
Up to 500 mm of rain was expected in the southern Kyushu region by 6 p.m. Sunday, 400 mm in the northern Kyushu region, the southern Kinki region and Mie Prefecture, and 250 mm along the Pacific coast of Shikoku, the agency said.
Meanwhile, the agency said the season's 18th typhoon emerged at 9 a.m. Saturday in the Marshall Islands in the Pacific.
Typhoon Sondga, the name of a river in Vietnam, had an atmospheric pressure of 998 hectopascals and winds of up to 64.8 kph near its center.