Evacuation advisories are in effect for tens of thousands of residents near Tokyo whose homes are risk from possible mudslides.
The Japanese Meteorological Agency warns of heavy rain and thunder, just a week after Typhoon Faxai knocked out power in many parts of Chiba Prefecture.
Weather officials say unstable atmospheric conditions brought torrential rain to the region on Monday morning.
Tateyama City advised all households, or about 46,000 people, to evacuate.
Minamiboso City issued the same advice to 35 residents. The area recorded 50 millimeters of rain in one hour from 9 a.m.