Average sea water temperature in September:
+73.8°F
| Minimum sea water temperature in September: | 82.6°F |
| Maximum sea water temperature in September: | 68.9°F |
Daily sea water temperature in September, °F
Show year:
2025
2024
2023
The average sea water temperature in September of 2025 was 75.2°F. The highest and lowest sea temperatures during the month were 77.5°F and 73.0°F.
Monthly sea water temperature in Koper, °F
Which Slovenia resorts have warmest sea in September?
| Place name | September 2025 | September 2024 |
|---|---|---|
| Portoroz | 75.3°F | 75.9°F |
| Piran | 75.3°F | 75.9°F |
| Strunjan | 75.2°F | 75.8°F |
| Koper | 75.2°F | 75.5°F |
| Isola | 75.1°F | 75.6°F |
| Cerkno | 73.6°F | 74.6°F |
| Bohinjsko Jezero | 73.3°F | 74.5°F |
| Dolenjske Toplice | 71.7°F | 72.0°F |
Best time for vacation in Koper
Koper on a weather map
Places in Slovenia:
Name
°F
24 Hours Forecast
Koper
Local time: 06:27
December 05, friday
0900
45°F
W
4 mph
4 mph
1200
50°F
SW
5 mph
5 mph
1500
48°F
SW
6 mph
6 mph
1800
45°F
SW
7 mph
7 mph
2100
39°F
SW
6 mph
6 mph
December 06, saturday
0000
39°F
SW
6 mph
6 mph
0300
43°F
SW
6 mph
6 mph
0600
46°F
SW
6 mph
6 mph
