The Hokuriku region and southern Tohoku entered the rainy season on June 20, 2026, according to the Japan Meteorological Agency [1].
The delayed arrival of the rainy season can disrupt agricultural schedules and water management systems across Honshu. This year's onset follows a period of atypical weather patterns that pushed the seasonal transition beyond its usual window.
A stationary rain front caused precipitation to spread across a wide area of Honshu [1]. This meteorological feature acted as the primary driver for the transition, though its positioning delayed the typical timing of the rainy season's start.
In the Hokuriku region of north-west Honshu, the transition occurred nine days later than the climatological average [2]. This shift represents a significant departure from the expected seasonal timeline for the area.
Southern Tohoku in north-east Honshu also experienced a delay, entering the rainy season eight days later than the climatological average [3]. While some forecasts previously suggested the southern part of the region might not enter the season until June 21, the agency confirmed the onset on June 20 [1].
The Japan Meteorological Agency said the rain front remained stationary over the island, contributing to the widespread wet weather observed this Saturday. Local authorities typically monitor these transitions closely to prepare for the increased risk of landslides, and flooding associated with the rainy season.
“The Hokuriku region and southern Tohoku entered the rainy season on June 20, 2026”
The delayed onset of the rainy season in these regions suggests a shift in the movement of the stationary rain front, which can lead to more intense precipitation once the season fully establishes. For Japan's agricultural sector, such delays may affect the timing of rice planting and other critical crop cycles, potentially impacting yields if the delayed rain is followed by extreme weather events.
