News Rainy season begins in Kanto and Central Japan

Our favourite season is upon us:

The JMA announced yesterday that the rainy season (梅雨 tsuyu) has officially begun in the Kanto-Koshin and Tokai regions. The start of the rainy season in Kanto-Koshin, which includes the Tokyo metropolitan area, was roughly in line with the average year. In the Tokai region, it arrived one day later than usual. A seasonal rain front was expected to bring wet weather to broad areas of the country over the coming days, with heavy rain forecast for parts of western and eastern Japan.

The rainy season reached the Amami and Okinawa regions in early May. Kyushu, Chugoku and Kinki entered the season earlier this month. In Okinawa and Amami, the prolonged rainy period normally lasts until around 21 June and 29 June, respectively. In most other parts of Japan, the rainy season usually continues until the middle or latter half of July.

Meanwhile, the agency on Sunday warned of landslides, flooding in low-lying areas and rising river levels for the Shikoku region, as well as lightning and strong winds in western Japan. With the low-pressure system accompanying a rain front moving east-northeast in the southern Kyushu region, warm and humid air is pouring into the system, making the atmospheric condition unstable, the agency said.

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The JMA also maintains climatological dates of the Baiu onset and withdrawal across Japan. Baiu (梅雨) is the on'yomi (音読み) reading of tsuyu. It is more formal and appears more often in meteorological, academic, or technical contexts.



According to this data, baiu will last until 17 July. A particularly interesting statistic is that rainfall during tsuyu varies far more than the dates themselves. Kanto has seen years with roughly half the normal rainfall and others with nearly twice the average.

Fukuoka entered the rainy season as a typhoon approached. Before the rainy season started, it was very hot, with temperatures climbing above 30°C (86°F). Now it's been raining all day, with temperatures hovering around 20°C (68°F) and humidity close to 80%.

One thing that brightens my mood is seeing the hydrangeas blooming in my garden.

Hiroyuki Nagashima said:

One thing that brightens my mood is seeing the hydrangeas blooming in my garden.

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Same here. One thing I noticed is that the ajisai in our small garden change their colours every year. It's a very deep purple this year.

Ok, so I asked ChatGPT:

Most ajisai (紫陽花), or hydrangeas, can change colour depending on soil conditions, but the change is not always dramatic every year. The main factor is soil acidity:

• acidic soil tends to produce blue flowers
• alkaline soil tends to produce pink or reddish flowers

This happens because aluminium in the soil becomes more available to the plant in acidic conditions. The pigment in the flowers reacts to it and shifts colour. White hydrangeas are the exception. They usually stay white regardless of soil chemistry. In gardens, the same plant may appear:

• more blue one year
• more purple the next
• pinker after soil treatments or changes in rainfall

Japanese gardeners sometimes intentionally manipulate this by adding sulphur for bluer flowers or lime for pinker ones.

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That's right. Japan has long maintained hydrangea temples and parks where people can enjoy the beautiful scenery of the rainy season, so I highly recommend visiting one if you have the chance.

"Hydrangea Paradise Overlooking Mikawa Bay Illuminates the Night – Limited-Time Spectacular Light-Up in June" (June 7, 2026)

Colorful hydrangeas are now in full bloom. Today, the start of the rainy season was officially announced for the Tokai, Kanto-Koshin regions. This scene comes from Katahara Onsen Hydrangea Village in Gamagori City, Aichi Prefecture.

For this month only, the hydrangea gardens are illuminated at night, allowing visitors to enjoy a completely different and more enchanting view than during the daytime. The vibrant colors of the blossoms create a magical atmosphere, transforming the gardens into a breathtaking spectacle after dark.

Enjoy this colorful "Hydrangea Paradise," a beautiful symbol of the arrival of Japan's rainy season.

【京都の紫陽花】柳谷観音（楊谷寺）：hydrangea and Yanagidanikannon Youkoku-ji Temple/花手水