In September warmest sea in Slovenia is usually observed in the following locations: Portoroz, Piran, Strunjan.
Table below shows the average sea water temperature for marine resorts of Slovenia in September for the last three years.
| Place name | September 2025 | September 2024 | September 2023 |
|---|---|---|---|
| Portoroz | 75.3°F | 75.9°F | 75.5°F |
| Piran | 75.3°F | 75.9°F | 75.5°F |
| Strunjan | 75.2°F | 75.8°F | 75.4°F |
| Koper | 75.2°F | 75.5°F | 75.5°F |
| Isola | 75.1°F | 75.6°F | 75.3°F |
| Cerkno | 73.6°F | 74.6°F | 74.3°F |
| Bohinjsko Jezero | 73.3°F | 74.5°F | 74.1°F |
| Dolenjske Toplice | 71.7°F | 72.0°F | 73.8°F |
Charts below show average sea water temperature for Slovenia resorts with the warmest sea in September.
You can also check other months of the year to see sea temperature of Slovenia resorts at that time.
Places in Slovenia:
Name
°F
