The Slovenia resorts with the warmest sea water temperature in December are Portoroz, Piran and Strunjan.
Below you can see a list of all popular Slovenia resorts and information about sea water temperature in December for the last two years.
| Resort Name | December 2025 | December 2024 | December 2023 |
|---|---|---|---|
| Portoroz | 57.6°F | 57.2°F | 57.3°F |
| Piran | 57.6°F | 57.2°F | 57.3°F |
| Strunjan | 57.3°F | 56.9°F | 57.0°F |
| Isola | 57.1°F | 56.6°F | 56.6°F |
| Dolenjske Toplice | 57.0°F | 57.9°F | 58.2°F |
| Koper | 56.7°F | 56.4°F | 56.3°F |
| Cerkno | 55.0°F | 54.5°F | 55.4°F |
| Bohinjsko Jezero | 54.8°F | 54.2°F | 55.3°F |
Please see following sea water temperature averages charts for the warmest Slovenia resorts in December.
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.
Slovenia Resorts:
NAME
F°
| Bohinjsko Jezero |  |
+40 |
| Cerkno | |
+44 |
| Dolenjske Toplice |  |
+38 |
| Isola | |
+48 |
| Koper | |
+48 |
| Kranjska Gora | |
+40 |
| Ljubljana | |
+46 |
| Maribor | |
+42 |
| Moravske Toplice | |
+42 |
| Piran | |
+48 |
| Portoroz | |
+48 |
| Rogaska Slatina | |
+42 |
| Strunjan | |
+48 |
| Terme Radenci | |
+42 |
| Zrece | |
+42 |
