The Japan resorts with the warmest sea water temperature in September are Okinawa, Nagasaki and Kobe.
Below you can see a list of all popular Japan resorts and information about sea water temperature in September for the last two years.
| Resort Name | September 2026 | September 2025 | September 2024 |
|---|---|---|---|
| Okinawa | 87.3°F | 89.9°F | 89.2°F |
| Nagasaki | 85.6°F | 87.7°F | 87.6°F |
| Kobe | 84.8°F | 85.0°F | 86.4°F |
| Osaka | 84.7°F | 86.1°F | 87.2°F |
| Nara | 84.2°F | 86.2°F | 87.3°F |
| Fukuoka | 83.8°F | 86.9°F | 86.2°F |
| Nagoya | 82.8°F | 85.7°F | 87.7°F |
| Hiroshima | 82.7°F | 84.9°F | 85.8°F |
| Kyoto | 82.6°F | 86.3°F | 87.8°F |
| Hakone | 81.4°F | 82.7°F | 84.5°F |
| Atami | 81.3°F | 83.0°F | 84.6°F |
| Tokyo | 81.2°F | 85.1°F | 85.5°F |
| Yokohama | 81.2°F | 84.3°F | 85.1°F |
| Kamakura | 81.0°F | 82.9°F | 84.4°F |
| Sapporo | 73.5°F | 75.8°F | 74.7°F |
| Noboribetsu | 70.8°F | 73.5°F | 73.9°F |
Please see following sea water temperature averages charts for the warmest Japan resorts in September.
You can also get the same information for the every other month of the year when the average sea water temperature is greater then 70°F.
