Average sea water temperature in September:
+74.0°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:
2026
2025
2024
The average sea water temperature in September of 2026 was 77.2°F. The highest and lowest sea temperatures during the month were 81.5°F and 73.2°F.
Monthly sea water temperature in Koper, °F
Which Slovenia resorts have warmest sea in September?
| Place name | September 2026 | September 2025 |
|---|---|---|
| Portoroz | 77.6°F | 75.3°F |
| Piran | 77.6°F | 75.3°F |
| Strunjan | 77.4°F | 75.2°F |
| Koper | 77.1°F | 75.2°F |
| Isola | 77.1°F | 75.1°F |
| Cerkno | 75.2°F | 73.6°F |
| Bohinjsko Jezero | 75.0°F | 73.3°F |
| Dolenjske Toplice | 74.6°F | 71.7°F |
Best time for vacation in Koper
Koper on a weather map
Places in Slovenia:
Name
°F
24 Hours Forecast
Koper
Local time: 01:37
October 27, tuesday
0300
45°F
W
5 mph
5 mph
0600
45°F
W
5 mph
5 mph
0900
54°F
W
4 mph
4 mph
1200
63°F
SW
2 mph
2 mph
1500
63°F
S
3 mph
3 mph
1800
50°F
W
4 mph
4 mph
2100
48°F
W
4 mph
4 mph
October 28, wednesday
0000
46°F
W
5 mph
5 mph
