In September warmest sea in Finland is usually observed in the following locations: Kotka, Lappeenranta, Lahti.
Table below shows the average sea water temperature for marine resorts of Finland in September for the last three years.
| Place name | September 2025 | September 2024 | September 2023 |
|---|---|---|---|
| Kotka | 61.4°F | 64.4°F | 62.6°F |
| Lappeenranta | 61.2°F | 64.4°F | 62.0°F |
| Lahti | 60.6°F | 62.4°F | 61.2°F |
| Turku | 60.5°F | 61.9°F | 61.3°F |
| Savolinna | 60.1°F | 62.9°F | 61.3°F |
| Vantaa | 59.5°F | 61.9°F | 61.9°F |
| Helsinki | 59.5°F | 61.7°F | 61.9°F |
| Juvaskyla | 59.5°F | 61.0°F | 60.1°F |
| Imatra | 59.4°F | 62.4°F | 61.1°F |
| Espoo | 59.3°F | 61.8°F | 61.8°F |
| Porvoo | 59.1°F | 61.9°F | 61.1°F |
| Koli National Park | 59.1°F | 61.5°F | 59.6°F |
| Vaasa | 57.7°F | 58.8°F | 58.5°F |
| Pori | 57.3°F | 60.1°F | 59.4°F |
| Seinajoki | 56.7°F | 58.0°F | 56.6°F |
| Oulu | 56.6°F | 58.0°F | 56.7°F |
| Kemi | 56.2°F | 58.2°F | 56.5°F |
| Saariselka | 53.1°F | 54.0°F | 53.4°F |
Charts below show average sea water temperature for Finland resorts with the warmest sea in September.
You can also check other months of the year to see sea temperature of Finland resorts at that time.
Places in Finland:
Name
°F
