Japanese summers are hot and wet, and the bath does not stop for them. It changes. Cooler water, and a plant that leaves the skin feeling cold in warm air.
Gyōzui行水
Before every home had hot water on tap, summer bathing happened outside. A tub was filled with warm water in the yard, and you washed or sat in it as the day cooled.
The custom is called gyōzui. It was everyday life from the Edo period until well into the twentieth century, and it is still a summer word in haiku.
Hakka薄荷
Hakka is Japanese mint. It carries more menthol than the mint most of Britain knows, and a hakka bath leaves the skin feeling cool as you step out into the evening.
Its story runs the length of Japan. Commercial growing began in Okayama and Hiroshima in the 1850s, moved north to Yamagata, then to Hokkaido. By 1938 the fields around Kitami produced around seven tenths of the world's mint. Cheaper imports and synthetic menthol ended that. A handful of growers kept going.
The cool is a feeling on the skin, not a drop in temperature. Japan's summer bath is about how the evening feels.
The evening cool夕涼み
The bath is only half of it. Afterwards comes yūsuzumi (夕涼み), the evening cool: sitting out in a light cotton robe with a fan, where the air moves. Somewhere nearby, a fūrin (風鈴), the glass wind chime, turns a breeze into a sound.
For a warming Britain
British summers are getting hotter. Japan has spent centuries working out how to rest in the heat, and a hot evening does not have to mean giving up the bath. It means changing it.