Sea temperature and swimming season in Japan
When the sea is warm enough to swim in 77 coastal cities in Japan.
| City | Warmest | Coldest | Swimming season |
|---|---|---|---|
| Tokyo | 27.5°C Aug | 11.5°C Jan | May – Oct (6 months) |
| Yokohama | 27.0°C Aug | 13.1°C Feb | May – Nov (7 months) |
| Osaka | 28.3°C Aug | 9.5°C Feb | Jun – Nov (6 months) |
| Kobe | 28.2°C Aug | 9.8°C Feb | Jun – Nov (6 months) |
| Chiba | 27.5°C Aug | 11.5°C Jan | May – Oct (6 months) |
| Kitakyushu | 28.0°C Aug | 13.8°C Feb | Jun – Nov (6 months) |
| Niigata | 27.8°C Aug | 10.4°C Mar | Jun – Nov (6 months) |
| Hamamatsu | 28.3°C Aug | 16.6°C Feb | May – Dec (8 months) |
| Shizuoka | 27.9°C Aug | 16.0°C Feb | May – Nov (7 months) |
| Kagoshima | 28.9°C Aug | 17.6°C Feb | Apr – Dec (9 months) |
| Himeji | 28.1°C Aug | 9.4°C Feb | Jun – Nov (6 months) |
| Matsuyama | 26.9°C Aug | 11.6°C Feb | Jun – Nov (6 months) |
| Fukuyama | 28.8°C Aug | 11.3°C Feb | Jun – Nov (6 months) |
| Kanazawa | 28.0°C Aug | 11.3°C Mar | Jun – Nov (6 months) |
| Yokosuka | 27.0°C Aug | 16.1°C Mar | May – Nov (7 months) |
| Nagasaki | 28.6°C Aug | 15.8°C Feb | May – Nov (7 months) |
| Toyohashi | 28.3°C Aug | 16.0°C Feb | May – Dec (8 months) |
| Iwaki | 24.8°C Aug | 13.6°C Mar | Jun – Nov (6 months) |
| Kochi | 28.8°C Aug | 17.1°C Feb | Apr – Dec (9 months) |
| Naha | 29.2°C Aug | 21.8°C Feb | all year |
| Yokkaichi | 28.8°C Aug | 10.1°C Feb | May – Nov (7 months) |
| Akashi | 28.2°C Aug | 9.9°C Feb | Jun – Nov (6 months) |
| Aomori | 24.5°C Aug | 7.2°C Mar | Jul – Oct (4 months) |
| Hakodate | 24.0°C Aug | 9.1°C Mar | Jul – Oct (4 months) |
| Tsu | 28.6°C Aug | 10.5°C Feb | Jun – Nov (6 months) |
| Tokushima | 27.6°C Aug | 11.1°C Feb | Jun – Nov (6 months) |
| Fuji | 27.8°C Aug | 15.6°C Feb | May – Nov (7 months) |
| Sasebo | 28.1°C Aug | 14.9°C Feb | May – Nov (7 months) |
| Chigasaki | 27.3°C Aug | 16.4°C Feb | May – Nov (7 months) |
| Saga | 28.9°C Aug | 11.2°C Feb | May – Nov (7 months) |
| Kure | 27.0°C Aug | 11.5°C Feb | Jun – Nov (6 months) |
| Matsue | 28.0°C Aug | 13.3°C Feb | Jun – Nov (6 months) |
| Numazu | 27.8°C Aug | 15.6°C Feb | May – Nov (7 months) |
| Jōetsu | 28.1°C Aug | 10.8°C Mar | Jun – Nov (6 months) |
| Odawara | 27.4°C Aug | 16.4°C Feb | May – Nov (7 months) |
| Tottori-shi | 28.0°C Aug | 12.5°C Feb | Jun – Nov (6 months) |
| Tomakomai | 22.1°C Aug | 3.0°C Mar | Aug – Sep (2 months) |
| Hitachi | 25.0°C Aug | 14.6°C Mar | Jun – Nov (6 months) |
| Ube | 28.4°C Aug | 9.9°C Feb | Jun – Nov (6 months) |
| Izumo | 28.0°C Aug | 13.8°C Feb | Jun – Nov (6 months) |
| Urayasu | 27.5°C Aug | 11.5°C Jan | May – Oct (6 months) |
| Kushiro | 19.2°C Aug | 0.6°C Feb | Aug – Aug (1 months) |
| Yonago | 28.1°C Aug | 13.0°C Feb | Jun – Nov (6 months) |
| Okinawa | 29.2°C Aug | 21.6°C Feb | all year |
| Ishinomaki | 25.0°C Aug | 9.1°C Mar | Jul – Oct (4 months) |
| Kisarazu | 27.0°C Aug | 13.3°C Feb | May – Nov (7 months) |
| Onomichi | 28.8°C Aug | 11.3°C Feb | Jun – Nov (6 months) |
| Iwakuni | 27.0°C Aug | 11.5°C Feb | Jun – Nov (6 months) |
| Ise | 28.6°C Aug | 10.5°C Feb | Jun – Nov (6 months) |
| Honmachi | 28.5°C Aug | 12.9°C Feb | May – Nov (7 months) |
| Karatsu | 28.2°C Aug | 14.1°C Feb | Jun – Nov (6 months) |
| Saijō | 28.5°C Aug | 11.4°C Feb | Jun – Nov (6 months) |
| Maizuru | 28.2°C Aug | 12.0°C Mar | Jun – Nov (6 months) |
| Sendai | 29.0°C Aug | 16.9°C Feb | May – Dec (8 months) |
| Fukuroi | 28.2°C Aug | 16.7°C Feb | May – Dec (8 months) |
| Kashiwazaki | 28.0°C Aug | 10.6°C Mar | Jun – Nov (6 months) |
| Yurihonjō | 27.1°C Aug | 9.8°C Mar | Jun – Oct (5 months) |
| Chiryū | 28.7°C Aug | 10.7°C Feb | May – Nov (7 months) |
| Yukuhashi | 28.7°C Aug | 9.7°C Feb | Jun – Nov (6 months) |
| Uwajima | 27.3°C Aug | 15.7°C Feb | May – Dec (8 months) |
| Itō | 27.6°C Aug | 16.8°C Mar | May – Dec (8 months) |
| Tōgane | 25.6°C Sep | 14.8°C Mar | Jun – Nov (6 months) |
| Asahi | 25.6°C Sep | 14.8°C Mar | Jun – Nov (6 months) |
| Nago | 29.2°C Aug | 21.4°C Feb | all year |
| Tokoname | 28.7°C Aug | 10.7°C Feb | May – Nov (7 months) |
| Mutsu | 23.6°C Sep | 8.5°C Mar | Jul – Oct (4 months) |
| Tateyama | 26.9°C Aug | 16.7°C Mar | May – Dec (8 months) |
| Ishigaki | 29.8°C Aug | 23.1°C Feb | all year |
| Uozu | 28.5°C Aug | 10.9°C Mar | Jun – Nov (6 months) |
| Kamaishi | 23.4°C Aug | 7.8°C Mar | Jul – Oct (4 months) |
| Misawa | 22.8°C Aug | 8.0°C Mar | Jul – Oct (4 months) |
| Abashiri | 19.9°C Aug | -1.2°C Feb | Aug – Aug (1 months) |
| Isumi | 26.5°C Sep | 16.7°C Mar | May – Dec (8 months) |
| Wakkanai | 21.0°C Aug | 4.6°C Feb | Aug – Sep (2 months) |
| Hirado | 28.2°C Aug | 14.6°C Feb | Jun – Nov (6 months) |
| Shingū | 28.4°C Aug | 17.4°C Feb | May – Dec (8 months) |
| Wajima | 27.7°C Aug | 11.1°C Mar | Jun – Nov (6 months) |
Knowing the temperature is only half of it. What to wear, and why cold shock is the real risk →
Season uses 19°C. Why that number, and where the data comes from