September weather forecastKoper, Slovenia
September
Weather in September
Koper's weather in September heralds the arrival of autumn, with a slight diminution in sea temperature to 23.3°C (73.9°F). The receding heat signals the end of the hot summer days, adding a hint of freshness in the air. Yet, the lingering warmth and extended daylight hours make September an appealing month for late summer visitors. The city maintains its vibrant atmosphere, as the summer slowly gives way to the soft touch of autumn.Sea temperature
In September, the average sea temperature in Koper, Slovenia, is 23.3°C (73.9°F).Note: The cold tolerance of an individual, along with sunshine, wind, and the temperature of the environment, affects the enjoyment of swimming in 23.3°C (73.9°F) waters. (Olympic swimmers participate in waters ranging from 25°C (77°F) to 28°C (82.4°F).)
Daylight
In Koper, the average length of the day in September is 12h and 32min.On the first day of the month, sunrise is at 06:27 and sunset at 19:42. On the last day of September, sunrise is at 07:02 and sunset at 18:47 CEST.
Updated: Jan 24, 2024
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Published by: Weather Atlas | About Us
Data Sources | Weather Forecasting & Climate
Frequently asked questions
In September, the average sea temperature in Koper is 23.3°C (73.9°F). For individuals prone to feeling cold, swimming in 23°C (73.4°F) is still regarded as intolerable. A wetsuit is not a necessity, but sunshine, wind, and air temperature are essential factors for relishing swimming at 23.3°C (73.9°F).
In Koper, Slovenia, the average day length in September is 12h and 32min.
In September, on the first day of the month, sunrise is at 06:27 and sunset at 19:42. On the last day of the month, sunrise is at 07:02 and sunset at 18:47 CEST.
Average sea temperature in September
Koper, Slovenia
- Average sea temperature in September: 23.3°C
The best months for swimming (with the highest average sea temperature) are July and August (24.8°C).
The coldest month (with the lowest average sea temperature) is February (9.3°C).
Average daylight in September
Koper, Slovenia
- Average daylight in September: 12h and 30min
The month with the longest days is June (Average daylight: 15h and 36min).
The month with the shortest days is December (Average daylight: 8h and 48min).





