The rainy season began Monday in Okinawa Prefecture and on Amami Island in Kagoshima Prefecture, the first areas of Japan to experience it this year, the Meteorological Agency said.
The rainy season began 10 days later than usual in Okinawa and eight days later on Amami Island, but four days earlier in both areas than last year, according to the agency.
The end of the rainy season in an average year is around June 23 in Okinawa and June 28 on Amami.
The rainfall is expected to help ease the strain on agriculture and water supply on Okinawa Island, where little rain has fallen since late April.
The city of Naha had precipitation of 11 mm between April 22 and May 14, only 7 percent of an average year. The Okinawa Meteorological Observatory has issued a warning over damage to agricultural products and called on farmers to manage water use carefully.
The agency predicts cloudy or rainy weather for most of the week ahead in those areas.