Rainy Season Officially Begins in Japan's Kanto-Koshin and Tokai Regions

On June 7, 2026, the Japan Meteorological Agency (JMA) announced that the Kanto-Koshin and Tokai regions have likely entered the rainy season. The arrival of the long-awaited wet season has quickly become a major topic of discussion across social media.

According to the JMA, the start of the rainy season in the Kanto-Koshin region is on par with an average year, though it comes 16 days later than last year. Meanwhile, the Tokai region saw its rainy season begin one day later than average and 21 days later than last year. Because last year featured an unusually early start, this year's transition feels considerably delayed, despite being right on schedule historically. On average, the rainy season in both regions ends around July 19.

Over the coming week, active weather fronts and humid air are expected to bring predominantly cloudy and rainy conditions. In recent years, climate change has increased the frequency of localized torrential downpours, "guerrilla rainstorms," and the formation of linear rainbands. These phenomena can trigger landslides and severe thunderstorms, making it essential for residents to stay updated with the latest disaster prevention alerts from the JMA and local governments.

The announcement has triggered a wide range of reactions online. While many social media users expressed dread over the upcoming humid weather and the struggle of drying laundry, others took a more positive view, calling it a "blessing for crops" and sharing tips on maintaining physical well-being. Because the sudden changes in humidity and atmospheric pressure can easily affect physical and mental health, managing indoor moisture and practicing self-care are highly recommended during this period.

Understanding Tsuyu: Japan's Rainy Season

The rainy season in Japan, known as "tsuyu" (literally "plum rain" because it coincides with the ripening of plums), is a seasonal weather pattern caused by the collision of cold northern and warm southern air masses. It typically spans from early June to mid-July for most of the Japanese archipelago, excluding Hokkaido.

While tsuyu is vital for the country's agricultural sector—particularly for rice cultivation, which requires abundant water—it also presents unique challenges. In recent years, meteorologists have frequently used the term "linear rainbands" (senjo-kousuitai) to describe rows of developed cumulonimbus clouds that remain stationary, bringing devastating, concentrated rainfall. Similarly, "guerrilla rainstorms" refer to sudden, unpredictable downpours in urban areas. Beyond safety hazards, Japanese residents also grapple with "tsuyu-darui" (rainy season fatigue), a term used to describe the physical sluggishness and headaches brought on by high humidity and fluctuating barometric pressure.