Meteo Santorini (Thira) in settembre

Regulars on the Santorini forum split September in two: the first half still runs on August's crowds and prices, and the back half — after most of Europe has gone home — is where the island actually loosens up, with a warm sea and a lot less queueing for the Oia sunset.

Regulars describe a real hinge partway through the month - the first half typically warm and sunny, with a storm often arriving mid-month that tips the rest of October toward cooler, more changeable weather, wind and cloud included even during the day. Our row backs the mild, still-mostly-dry read, 23.1C over 17.7C nights feeling 15C, with rain still minimal overall at 8.8mm across 1.7 days despite that mid-month risk. Regulars are consistent everything stays genuinely open this month, with far fewer tourists than peak summer, though a sweater and a lined wind jacket are standard advice for cooling evenings regardless of which half of the month you land in. The sea stays warm from summer at 23.6C. The record: humidity 72 percent, 9.9 hours of sun, a 30.3 kph wind and AQI 47.

July is genuinely hot here, up toward 40C on a bad day, and regulars credit the meltemi - the north wind that picks up specifically in July and August - with keeping it from feeling worse than it does. Our row backs the heat and the wind both, 30C reading as 31C under a real 33.3 kph average, with rain a rounding error at 0.1mm for the whole month. The meltemi's real cost is to travel rather than comfort: it can ground the small high-speed catamarans between islands, though a large conventional car ferry rarely gets stuck, and one regular with fifty-plus Greek ferry trips reported only a single wind cancellation across them. The sea is 24.5C. The record: humidity 73 percent, 13.1 hours of sun and AQI 67.

The meltemi is at its hardest in early August and regulars are split about it in a useful way: it is unpredictable and can be a nuisance, and it is also the only thing keeping the month bearable, because August here is scorching and the wind does not cool you until the sun is down. Our row measures it at 31.8 kph under 29.7C. The other August figure is the traffic: cruise activity peaks now, with as many as twelve ships in and out on a single day, and the thinning at the end of the month is not enough to feel. Late August does bring the year's warmest sea, ours at 25.9C. The record: 24C nights, 1.1mm of rain, 12.6 hours of sun and AQI 64.

Consensus on the forum is that March is still deep off-season: cold, windy, and quiet, with one traveler describing a late-March week as cold, windy and rainy all at once. Others push back that it's not uniformly bad - some days are genuinely pleasant - but the general steer is that mid-March can still be very cold, wet and windy, and if your dates are flexible, waiting another 4-6 weeks makes a real difference. More than 100 hotels do stay open through winter, just with a much reduced range of shops and restaurants running.