The Japan Meteorological Agency said Northern Kyushu, Chugoku, and Kinki have officially entered the rainy season [1].
This transition marks the beginning of a period of increased precipitation and instability across western Japan. The timing is critical for agricultural planning and disaster preparedness, as the region faces a heightened risk of flooding and landslides during the seasonal shift.
According to the agency, Kyushu entered the rainy season two days earlier than the climatological average [1]. While some areas in Kinki may see sunshine, rain is expected in parts of the region, and across Shikoku [1], [2].
Meteorologists are monitoring a tropical low pressure system forecast to move north over the weekend [1]. This system is expected to bring additional moisture, creating a risk of heavy rain. Reports vary on the system's precise path, with some indicating it will move toward Honshu's Pacific side and others suggesting it will move toward northern Japan [1], [2].
Daily temperature forecasts show a range of conditions across the archipelago. In the south, Naha is expected to reach 30 °C [1]. Other major cities include Osaka at 29 °C [1], Niigata at 28 °C [1], and Okayama at 28 °C [1].
Central and northern regions remain cooler. Tokyo is forecast to reach 24 °C [1], while Sendai and Aomori are expected to hit 23 °C [1]. In the far north, Sapporo is forecast at 24 °C [1], and Kushiro is expected to reach 16 °C [1].
Other regional forecasts include Nagoya at 26 °C [1], Kanazawa at 26 °C [1], and Nagano at 25 °C [1]. In the west, Matsue is forecast at 26 °C [1], Kochi at 27 °C [1], and Fukuoka at 24 °C [1]. Kagoshima is expected to reach 25 °C [1].
The agency said the rainy season front is currently advancing over western Japan, which is driving the current weather patterns [1].
“Kyushu entered the rainy season two days earlier than the climatological average”
The early arrival of the rainy season in Kyushu, combined with an approaching tropical low, suggests a volatile start to the season. The discrepancy in forecasts regarding the low pressure system's path emphasizes the unpredictability of this year's moisture transport, which could lead to localized extreme weather events across both Honshu and the southern islands.
