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Warmest sea in Japan in September

373 coastal locations in Japan ranked by their typical September sea temperature. Region-wide average in September: 25.8°C. The top of the list is where to find the warmest swimming this month.

Warmest in September

Minami-Tori Shima

29.5°C September mean in Japan

Regional September average

25.8°C

across all 373 coastal locations in Japan

Vs annual mean

+6.7°C

above the year-round regional average

What the Japan sea feels like in September

This water temperature is comparable to that of a swimming pool, but it might be higher than most open water swimmers prefer for serious swimming. Make sure to drink plenty of water before and after swimming and don't wear a wetsuit to avoid overheating.

Japan monthly average 12.8°C to 26.6°C
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  • Warmest month August 26.6°C
  • Coldest month February 12.8°C
  • Annual mean 19.1°C
  • Months above 20°C 5 of 12

Where September fits in the year

September sits inside the regional pattern shown on the left. Pick a different month to see how the ranking shifts.

All twelve Japan month rankings:

Japan sea temperature map (live)

The map shows today's latest reading at every Japan location. The list below is based on the typical September mean, useful for trip planning weeks or months ahead.

Zoom in to see individual locations. Click a pin for water temperatures. View list →
°C -2 0 1 3 5 7 9 11 13 15 17 19 21 24 27 30 35

Top 50 warmest Japan locations in September

Sorted by the typical September mean built from a decade of daily readings at each location. Click any place for its 30-day chart, monthly profile, and full 10-year history.

# Location September mean
1 Minami-Tori Shima Tokyo 29.5°C
2 lo Shima Tokyo 29.4°C
3 Minami-Daito Shima Okinawa 29.3°C
4 Yonakuni Shima Okinawa 29.2°C
5 Fuji 29.2°C
6 Haha Shima Tokyo 29.2°C
7 Funauke Okinawa 29.1°C
8 Wadomari Kagoshima 29.1°C
9 Tsuhako Okinawa 29.1°C
10 Miyakojima 29.1°C
11 Hirara Okinawa 29.1°C
12 Ishigaki 29.1°C
13 Kanegusuku Okinawa 29.1°C
14 Yonakuni 29.0°C
15 Sanmura Wan Kagoshima 29.0°C
16 Naha Ko Okinawa 29.0°C
17 Suku Okinawa 29.0°C
18 Chichi Shima Tokyo 29.0°C
19 Takara Shima Kagoshima 29.0°C
20 Haebaru 29.0°C
21 Itoman 29.0°C
22 Kerama Kaikyo (Zamami) Okinawa 29.0°C
23 Okinawa 29.0°C
24 Tomigusuku 29.0°C
25 Amami 29.0°C
Show 25 more ▸
26 Chatan 29.0°C
27 Gushikawa 29.0°C
28 Nago 29.0°C
29 Nakano Shima Kagoshima 29.0°C
30 Gakiya Okinawa 28.9°C
31 Toguchi Okinawa 28.9°C
32 Tori Shima Tokyo 28.9°C
33 Koniya Kagoshima 28.9°C
34 Kobi Sho Okinawa 28.8°C
35 Uken Kagoshima 28.8°C
36 Kasari Wan Kagoshima 28.8°C
37 Kuchi-No-Erabu Shima Kagoshima 28.8°C
38 Ogasawara 28.7°C
39 Isso Kagoshima 28.6°C
40 Kumano Kagoshima 28.5°C
41 Hachijo Jima Tokyo 28.4°C
42 Yakushima 28.4°C
43 Me Shima Nagasaki 28.2°C
44 Odomari Kagoshima 28.1°C
45 Yamagawa Kagoshima 28.1°C
46 Makurazaki 28.1°C
47 Nishinoomote 28.1°C
48 Kagoshima Kagoshima 28.1°C
49 Kiire Kagoshima 28.1°C
50 Tarumizu 28.0°C

Coldest 10 in Japan in September

Same data the other way. Helpful if you want to know which Japan coasts to avoid for swimming in September.

# Location September mean
1 Moyoro Wan Hokkaido 13.8°C
2 Hitokappi Wan Hokkaido 14.8°C
3 Mikuni 15.2°C
4 Muta 15.2°C
5 Shibetoro Hokkaido 15.3°C
6 Shana Wan Hokkaido 15.9°C
7 Naibo Wan Hokkaido 15.9°C
8 Hanasaki Hokkaido 17.4°C
9 Nemuro Ko Hokkaido 17.4°C
10 Kiritappu Hokkaido 17.6°C

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