The Japan Meteorological Agency said on June 21 that northern Tohoku has officially entered the rainy season [1].
The delayed onset of the rainy season combined with specific atmospheric conditions increases the risk of sudden flooding and landslides across several regions. This weather pattern poses a significant threat to local infrastructure and agriculture in northern Japan.
According to the agency, the start of the rainy season is six days later than the historical average [1]. This shift in timing coincides with an influx of moist air from Typhoon No. 7, which is currently located in the waters east of the Philippines [2]. This moisture is flowing into the seasonal rain front, heightening the probability of heavy precipitation.
Forecasters expect rain to continue through June 22 in both the Tohoku and Hokuriku regions [1]. The agency said that expected precipitation could reach a maximum of 120 mm in the Tohoku region [1]. Meanwhile, the Hokuriku region is expected to see a maximum of 100 mm [1].
Local authorities are monitoring the situation as the moist air continues to fuel the rain front. The agency said that the risk of heavy rain remains elevated for both North Japan and the Hokuriku area through the end of the current forecast period.
Residents in these areas are advised to stay alert for weather warnings and potential evacuation orders. The combination of a late start and high moisture levels often leads to more volatile weather patterns than those seen during a standard seasonal transition.
“the start of the rainy season is six days later than the historical average”
The delayed arrival of the rainy season in northern Tohoku, coupled with the influence of Typhoon No. 7, creates a high-risk scenario for extreme precipitation. When a seasonal front is reinforced by tropical moisture, the resulting rainfall is often more intense than typical seasonal rains, increasing the likelihood of flash floods and soil instability in mountainous regions.
