Northern Japan is expected to see heavy rains through this afternoon, and the Meteorological Agency on Sunday issued warnings of landslides and flooding in the region.
Weather officials said 80-120 mm of rain is expected for the Tohoku region in northeastern Japan and some parts of Hokkaido, Japan's northernmost main island.
The agency said weather systems have become unstable as warm, humid air in the south has streamed toward low atmospheric pressure in the Sea of Japan.
Torrential rains of around 30 mm per hour fell early Sunday in regions ranging from Tokai to Tohoku, according to the agency.
The agency issued heavy rain warnings for the Izu islands of Niijima and Miyake Island, some 150 to 200 km south of Tokyo. The islands have been hit by a series of strong earthquakes and volcanic eruptions recently.