The primary rainband of the East Asian Meiyu is displaced northward overall

High temperatures arrive earlier than usual in central and southern Japan

It is forecasted that over the next week, influenced by the combined effects of a northeastern cold vortex and a subtropical high (Figure 1), heavy to torrential rain will impact regions including North Korea, South Korea, the western coastal areas of Japan, the Tohoku region, Hokkaido Island, and the southern part of the Russian Far East. Specifically, parts of eastern North Pyongan Province and North Hwanghae Province in North Korea, southern South Korea and Gyeonggi Province, and western Tohoku region in Japan are expected to experience extremely heavy rain. The cumulative precipitation in these areas could reach 110-180 mm (Figure 2), accompanied by severe convective weather such as short-duration intense rainfall, thunderstorms with strong winds, and hail. The rainfall event in North Korea is anticipated from the 19th to the 21st, in South Korea and Japan from the 21st to the 24th, and in the Russian Far East from the 18th to the 22nd.

Additionally, under the persistent influence of the subtropical high-pressure system, a prolonged high temperatures is expected in central and southern Japan over the next ten days, with maximum temperatures generally exceeding 32°C. Specifically, the Kinki region and the eastern part of the Tohoku region are forecasted to experience daily highs surpassing 35°C, while the Kanto region and southern parts of the Chubu region may see daily maximum temperatures exceeding 37°C, approaching or surpassing historical records for the same period (Figure 3).

Figure 1. Average Geopotential Height at 500 hPa (Contour Lines, Units: dagpm) and Wind Field at 850 hPa (Wind Barbs, Units: m/s) from June 18 to 24, 2025

Figure 2. Forecasted Accumulated Precipitation from June 18 to 24, 2025 (Unit: mm)

Figure 3. Forecast of Daily Maximum Temperatures from June 18 to 27, 2025 (Unit: °C)

Author: Huo Da                                 Reviewer: Ma Jie 

English reviewer:Wang Yi                                                                       Issue approver:Dai Kan