September weather forecast and climate
Alderney, Guernsey GG

• Average sea temperature in September: 17.4°C

The best month for swimming (with the highest average sea temperature) is September (17.4°C).
The coldest month (with the lowest average sea temperature) is March (9.3°C).

• Average daylight in September: 12.6h

The month with the longest days is June (Average daylight: 16.2h).
The month with shortest days is December (Average daylight: 8.2h).