Weather in September
September begins to signify the end of summer, ushering
Alderney into the first hints of autumn. A marked drop is exhibited in daylight hours, coming down to an average of 12.6 per day. There's a minimal shift in sea temperature hovering at 17.4°C (63.3°F), exhibiting the highest sea temperature. September serves as a wonderful transitional month, retaining the warmth of the departing summer and introducing the crispness of the incoming autumn.
Sea temperature
September is the month with the warmest seawater, with an average sea temperature of 17.4°C (63.3°F).
Note: The majority find it unenjoyable to swim in 17.4°C (63.3°F). Breathing becomes tougher as the water temperature descends under 21°C (69.8°F).
Daylight
The average length of the day in September is 12h and 36min.
On the first day of the month, sunrise is at 06:25 and sunset at 19:52. On the last day of September, sunrise is at 07:08 and sunset at 18:49 BST.