The Japan Meteorological Agency announced the start of the rainy season for the Kanto-Koshin and Tokai regions on June 7 [1].
The onset of the rainy season, or tsuyu, brings critical risks of flooding and landslides that can disrupt transportation and threaten residential areas. Officials are monitoring weather patterns closely to prevent casualties during this volatile transition.
The agency made the official announcement at 11 a.m. JST [1]. According to the agency, the start of the season in Kanto-Koshin is on schedule with the long-term average [2]. The Tokai region's rainy season began one day later than the long-term average [2].
Weather officials said that a low-pressure system and an active frontal zone are currently moving along the southern coast of Japan. This atmospheric combination is producing intense rainfall across several prefectures, prompting the agency to issue landslide warnings.
While the rainy season has officially arrived in the east, western Japan remains under threat. The agency warned of heavy rain in Kyushu, Shikoku, and the southern Kii Peninsula [1].
"Strict vigilance against sediment-related disasters is necessary," the Japan Meteorological Agency said [1].
The agency is urging residents in the affected western regions to remain alert for sudden increases in water levels. Local governments are coordinating with the meteorological office to ensure evacuation routes are clear, and warning systems are operational as the frontal zone continues to shift.
“The start of the season in Kanto-Koshin is on schedule with the long-term average.”
The arrival of the rainy season in the Kanto-Koshin and Tokai regions marks the transition to Japan's most hazardous weather period. The simultaneous risk of heavy rain in western Japan suggests a widespread atmospheric instability that could lead to systemic infrastructure strain and increased emergency response requirements across the archipelago.
