- Published
- 9 April 2026
- Reading
- 4 min read
- Where
- Naxos, Greece
On the Cyclades the sea is warmest in August. In September it matches July, in October it matches June — except that an October day is over three hours shorter than a June one.
Greece in October has a June sea, not an August one. On the Cyclades the water is warmest in August, at around 24 °C; September holds July's temperature, and October drops back to 21.5–22 °C, where the sea stood at the start of summer.
Verdict — September is July, October is June. Average sea temperature in °C. Crete is measured off Heraklion; Naxos is the average of the last ten years.
The decision follows on its own. If June water is warm enough for you, October is the same. If you only get in once it's August, October isn't your month — take September, which has a July sea. September has another advantage: the meltemi, the northerly that peaks from mid-July to mid-August and can cancel ferry sailings, is easing by then, though it can still blow.
What October doesn't give back is daylight. On Naxos in mid-October the day lasts 11 hours 20 minutes, three hours 20 minutes less than in mid-June, and the clocks go back on the last Sunday of the month. The water is June's, but swimming belongs to the afternoon, not the evening.
This story is set on Naxos, and for October that's no accident. Naxos is the largest of the Cyclades, 430 square kilometres, with 20,578 residents at the 2021 census, and the most self-sufficient island in the group: it has water and fertile land, hence its own arseniko cheese, potatoes, honey and kitron liqueur. Out of season the difference shows — an island with work besides visitors still has a life once the visitors leave.
Ferries run from Piraeus to Naxos all year, 3 hours 15 minutes on a fast boat, longer on a conventional one. After September there are fewer sailings, and ticket sites don't agree on how many, so check the timetable for your dates before you book a room. With fewer sailings, a multi-island plan hangs on every connection; one or two islands are the safer bet.
If you want warmer water in October, go south rather than to another Cycladic island. Crete is the only place in the table where the October sea is warmer than June's.
October on the Cyclades doesn't suit anyone who wants 24-degree water (that's August), a swim after seven in the evening (that's June or July) or a five-island plan with tight connections. If a June sea is enough and you can live with a shorter day and fewer boats, you get the same sea as at the start of summer.
Greece, in brief
What now
If this sounds like your trip, start here.
- If June water is warm enough for you, go in October; if you only swim in August, take September — the sea then matches July.
- Plan swims for the afternoon: in mid-October the sun sets on Naxos around 18:45, and around 17:30 once the clocks go back.
- Check the Piraeus–Naxos timetable for your dates before booking a room — there are fewer sailings after September.
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