Is it warm enough to swim in Alonnisos in September? Average water temperature in Alonnisos in September is 24.7°C and therefore suitable for comfortable swimming. The warmest sea in Alonnisos in September is 28.1°C, and the coldest is 21.4°C. Average high air temperature in Alonnisos in September is 25°C, and average low temperature is 16°C. To find out the sea temperature today and in the coming days, go to Current sea temperature in Alonnisos
To get an accurate forecast for the water temperature in Alonnisos for any chosen month, compare two years within a 10 year range using the chart below. In addition to the sea water temperature in Alonnisos, the selected years in the table also show the values of the maximum and minimum temperatures on each of the days of September.
Day | 2025 | 2024 | Min | Max |
---|---|---|---|---|
1 September | 25.4°C | 27°C | 24.6°C | 28.1°C |
2 September | 25.7°C | 26.6°C | 24.7°C | 27.5°C |
3 September | 26°C | 26.5°C | 24.6°C | 27.1°C |
4 September | 25.8°C | 27°C | 25°C | 27°C |
5 September | 25.6°C | 27°C | 24.6°C | 27°C |
6 September | 26.6°C | 24.8°C | 26.8°C | |
7 September | 27°C | 24.7°C | 27°C | |
8 September | 26.7°C | 24.4°C | 26.7°C | |
9 September | 26.4°C | 23.9°C | 26.4°C | |
10 September | 26.7°C | 23.8°C | 26.7°C | |
11 September | 26.8°C | 23.8°C | 26.8°C | |
12 September | 26.8°C | 23.6°C | 26.8°C | |
13 September | 27°C | 23.6°C | 27°C | |
14 September | 26.6°C | 23.5°C | 26.6°C | |
15 September | 26.4°C | 23.7°C | 26.4°C |
Day | 2025 | 2024 | Min | Max |
---|---|---|---|---|
16 September | 26.3°C | 23.6°C | 26.3°C | |
17 September | 26.2°C | 23.5°C | 26.2°C | |
18 September | 26°C | 23.5°C | 26°C | |
19 September | 25.6°C | 23.6°C | 25.6°C | |
20 September | 25.5°C | 23°C | 25.5°C | |
21 September | 25.2°C | 22.7°C | 25.2°C | |
22 September | 25.1°C | 22.9°C | 25.1°C | |
23 September | 25.1°C | 22.7°C | 25.1°C | |
24 September | 25°C | 22.5°C | 25.1°C | |
25 September | 24.8°C | 22.4°C | 24.8°C | |
26 September | 25.2°C | 22.5°C | 25.2°C | |
27 September | 25.2°C | 22.3°C | 25.2°C | |
28 September | 25.2°C | 22.2°C | 25.2°C | |
29 September | 24.9°C | 21.4°C | 24.9°C | |
30 September | 24.7°C | 21.4°C | 24.7°C |
2015 | 2016 | 2017 | 2018 | 2019 |
25.3°C | 24.2°C | 24.7°C | 25.4°C | 24.5°C |
2020 | 2021 | 2022 | 2023 | 2024 |
25.2°C | 25°C | 24.9°C | 24.3°C | 26°C |
Chart comparing the height of waves in Alonnisos in September over the past years. The red line indicates the height of the waves when swimming in the sea is prohibited. To view the current sea conditions, click on the graph.
This data display average monthly climate indicators in Alonnisos in September based on our historical weather readings over a period of ten years. In addition to temperature, we include data on the number of rainy and sunny days so you can have all the information about your destination before your trip
You can also view information about water temperature for other months by clicking on the month button below