Heavy rain hits southwestern Japan, increasing disaster risk.

Heavy rain hit southern Kyushu in southwestern Japan on Sunday, prompting the weather agency to warn of possible landslides, flooding in low-lying areas and swollen or overflowing rivers.

Linear rainbands — zones of heavy rain clouds that form in succession over the same area — had developed in Miyazaki and Kagoshima prefectures through late Sunday morning, sharply increasing the risk of disasters, the Japan Meteorological Agency said.

Atmospheric conditions are likely to remain highly unstable across western Japan, with Shikoku, one of Japan’s four main islands, also possibly facing rainfall heavy enough to trigger warnings, the agency added.

According to the agency, a weather front extends from the Chinese mainland through the Nansei Islands in southwestern Japan to the south of the country, while a low-pressure system over the East China Sea along the front is moving east-northeast.

Warm, moist air is flowing toward the front and low-pressure system, causing heavy rain with thunder in parts of western Japan and the Nansei Islands.

By 6 a.m. Monday, rainfall in the 24-hour period is expected to reach up to 300 millimeters in Shikoku and 150 mm in southern Kyushu and the Amami region.

The agency, meanwhile, said Sunday that the Tokai region in central Japan and the Kanto-Koshin region including Tokyo, both on the main island of Honshu, appear to have entered the rainy season, which typically ends there in mid- to late July.

The rainy season is believed to have begun one day later than usual in Tokai and 21 days later than last year, while in Kanto-Koshin it started around the usual date but 16 days later than a year earlier, the agency said.

Cloudy and rainy weather is prevailing in both regions, with similar conditions forecast over the coming week as a front and moist air affects the areas, it added.