Japan's Kanto and Tokai regions are entering their annual rainy season as of early June [2].

The onset of the rainy season, or *tsuyu*, significantly impacts daily life for millions of residents. The transition brings a shift in weather patterns that affects everything from urban commuting and laundry routines to agricultural planning in these key economic hubs.

The Japan Meteorological Agency said it expects the Kanto-Koshin region to enter the rainy season around June 5 [2]. This timeline aligns with earlier projections from Weathernews, which released its 2026 outlook on May 13 [1]. A spokesperson for Weathernews said the rainy season for Kanto and Tokai was expected to occur in early June [1].

While most agencies align on an early June start, some discrepancies exist in the timing. While the Japan Meteorological Agency points toward June 5 [2], other reports from Tenki.jp suggested the rainy season could have arrived as early as May 20 [contradiction].

Other regions of the country have already seen seasonal shifts. A meteorological expert said that Okinawa and Amami entered the rainy season earlier than average [3]. In a contrast of weather extremes, the expert said that the Kanto-Koshin region was expected to record its first midsummer day [3].

Regarding the duration of the season, current projections suggest the 2026 rainy period will be average in length, or slightly shorter, across Japan [1]. Residents in the Kanto and Tokai areas are now preparing for a period of consistent precipitation and increased humidity.

“Kanto and Tokai are expected to enter the rainy season around June 5 2026”

The arrival of the rainy season in Kanto and Tokai marks a critical climatic transition for Japan's most populous regions. While the projection of an average or shorter season may mitigate some long-term flood risks, the immediate shift to high humidity and frequent rain disrupts urban logistics and consumer behavior. The variation in start dates between agencies highlights the volatility of the 2026 seasonal transition, particularly as some areas experience midsummer heat alongside the onset of heavy rains.