canIswim

What wetsuit do you need in Japan?

The one suit that covers most of the swimming season, for 76 coastal cities in Japan.

City Coldest Warmest One suit for the season
Tokyo 11.5°C Jan 27.5°C Aug nothing
Yokohama 13.1°C Feb 27.0°C Aug nothing
Osaka 9.5°C Feb 28.3°C Aug nothing
Kobe 9.8°C Feb 28.2°C Aug nothing
Chiba 11.5°C Jan 27.5°C Aug nothing
Kitakyushu 13.8°C Feb 28.0°C Aug nothing
Niigata 10.4°C Mar 27.8°C Aug nothing
Hamamatsu 16.6°C Feb 28.3°C Aug nothing
Shizuoka 16.0°C Feb 27.9°C Aug nothing
Kagoshima 17.6°C Feb 28.9°C Aug nothing
Himeji 9.4°C Feb 28.1°C Aug nothing
Matsuyama 11.6°C Feb 26.9°C Aug nothing
Fukuyama 11.3°C Feb 28.8°C Aug nothing
Kanazawa 11.3°C Mar 28.0°C Aug nothing
Yokosuka 16.1°C Mar 27.0°C Aug nothing
Nagasaki 15.8°C Feb 28.6°C Aug nothing
Toyohashi 16.0°C Feb 28.3°C Aug nothing
Iwaki 13.6°C Mar 24.8°C Aug nothing
Kochi 17.1°C Feb 28.8°C Aug nothing
Naha 21.8°C Feb 29.2°C Aug nothing
Yokkaichi 10.1°C Feb 28.8°C Aug nothing
Akashi 9.9°C Feb 28.2°C Aug nothing
Aomori 7.2°C Mar 24.5°C Aug nothing, or a rash vest
Hakodate 9.1°C Mar 24.0°C Aug nothing, or a rash vest
Tsu 10.5°C Feb 28.6°C Aug nothing
Tokushima 11.1°C Feb 27.6°C Aug nothing
Fuji 15.6°C Feb 27.8°C Aug nothing
Sasebo 14.9°C Feb 28.1°C Aug nothing
Chigasaki 16.4°C Feb 27.3°C Aug nothing
Saga 11.2°C Feb 28.9°C Aug nothing
Kure 11.5°C Feb 27.0°C Aug nothing
Matsue 13.3°C Feb 28.0°C Aug nothing
Numazu 15.6°C Feb 27.8°C Aug nothing
Jōetsu 10.8°C Mar 28.1°C Aug nothing
Odawara 16.4°C Feb 27.4°C Aug nothing
Tottori-shi 12.5°C Feb 28.0°C Aug nothing
Tomakomai 3.0°C Mar 22.1°C Aug nothing
Hitachi 14.6°C Mar 25.0°C Aug nothing
Ube 9.9°C Feb 28.4°C Aug nothing
Izumo 13.8°C Feb 28.0°C Aug nothing
Urayasu 11.5°C Jan 27.5°C Aug nothing
Kushiro 0.6°C Feb 19.2°C Aug nothing, or a rash vest
Yonago 13.0°C Feb 28.1°C Aug nothing
Okinawa 21.6°C Feb 29.2°C Aug nothing
Ishinomaki 9.1°C Mar 25.0°C Aug nothing
Kisarazu 13.3°C Feb 27.0°C Aug nothing
Onomichi 11.3°C Feb 28.8°C Aug nothing
Iwakuni 11.5°C Feb 27.0°C Aug nothing
Ise 10.5°C Feb 28.6°C Aug nothing
Honmachi 12.9°C Feb 28.5°C Aug nothing
Karatsu 14.1°C Feb 28.2°C Aug nothing
Saijō 11.4°C Feb 28.5°C Aug nothing
Maizuru 12.0°C Mar 28.2°C Aug nothing
Sendai 16.9°C Feb 29.0°C Aug nothing
Fukuroi 16.7°C Feb 28.2°C Aug nothing
Kashiwazaki 10.6°C Mar 28.0°C Aug nothing
Yurihonjō 9.8°C Mar 27.1°C Aug nothing
Chiryū 10.7°C Feb 28.7°C Aug nothing
Yukuhashi 9.7°C Feb 28.7°C Aug nothing
Uwajima 15.7°C Feb 27.3°C Aug nothing, or a rash vest
Itō 16.8°C Mar 27.6°C Aug nothing
Tōgane 14.8°C Mar 25.6°C Sep nothing
Asahi 14.8°C Mar 25.6°C Sep nothing
Nago 21.4°C Feb 29.2°C Aug nothing
Tokoname 10.7°C Feb 28.7°C Aug nothing
Mutsu 8.5°C Mar 23.6°C Sep nothing, or a rash vest
Tateyama 16.7°C Mar 26.9°C Aug nothing
Uozu 10.9°C Mar 28.5°C Aug nothing
Kamaishi 7.8°C Mar 23.4°C Aug nothing, or a rash vest
Misawa 8.0°C Mar 22.8°C Aug nothing, or a rash vest
Abashiri -1.2°C Feb 19.9°C Aug nothing, or a rash vest
Isumi 16.7°C Mar 26.5°C Sep nothing
Wakkanai 4.6°C Feb 21.0°C Aug nothing, or a rash vest
Hirado 14.6°C Feb 28.2°C Aug nothing
Shingū 17.4°C Feb 28.4°C Aug nothing
Wajima 11.1°C Mar 27.7°C Aug nothing

Thicknesses above are for swimming. Surfing the same water wants a step more — most of a session is spent sitting still in the wind rather than moving and immersed. Each city page gives both, along with when you need boots, gloves and a hood.

Sea temperature and swimming season in Japan →

Boots below 14°C, gloves below 12°C, a hood below 10°C. Where the numbers come from