The short answer: 15 May to 25 June. Across 26 summers, not a single meltemi episode lasting three days or more was recorded between 15 May and 11 June in the central Cyclades. After that the meltemi settles in — and it has two walls, not one.
At a glance
Best week 5 June – 11 June — ×0.2 (1.1 % hard days, 2/26).
Week to avoid 4 Sept – 10 Sept — ×2.3 (11.5 %, 12/26).
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| Week | Wind risk | Hard days | Summers affected | Sea | Daylight |
|---|---|---|---|---|---|
| 15 May – 21 May | ×0.4 | 2.2 % | 3/26 | 18.9 °C | 14.2 h |
| 22 May – 28 May | ×0.3 | 1.6 % | 2/26 | 20.0 °C | 14.4 h |
| 29 May – 4 June | ×0.4 | 2.2 % | 3/26 | 20.8 °C | 14.5 h |
| 5 June – 11 June | ×0.2 | 1.1 % | 2/26 | 21.9 °C | 14.6 h |
| 12 June – 18 June | ×0.4 | 2.2 % | 2/26 | 22.6 °C | 14.7 h |
| 19 June – 25 June | ×0.4 | 2.2 % | 3/26 | 22.7 °C | 14.7 h |
| 26 June – 2 July | ×1.1 | 5.5 % | 8/26 | 22.9 °C | 14.7 h |
| 3 July – 9 July | ×1.3 | 6.6 % | 7/26 | 23.6 °C | 14.6 h |
| 10 July – 16 July | ×1.1 | 5.5 % | 5/26 | 23.8 °C | 14.5 h |
| 17 July – 23 July | ×2.0 | 9.9 % | 8/26 | 24.7 °C | 14.4 h |
| 24 July – 30 July | ×1.1 | 5.5 % | 5/26 | 25.4 °C | 14.2 h |
| 31 July – 6 Aug | ×1.0 | 4.9 % | 6/26 | 25.5 °C | 14.0 h |
| 7 Aug – 13 Aug | ×0.7 | 3.3 % | 5/26 | 25.6 °C | 13.8 h |
| 14 Aug – 20 Aug | ×1.9 | 9.3 % | 10/26 | 25.6 °C | 13.6 h |
| 21 Aug – 27 Aug | ×1.0 | 4.9 % | 4/26 | 25.7 °C | 13.3 h |
| 28 Aug – 3 Sept | ×1.1 | 5.5 % | 6/26 | 25.4 °C | 13.1 h |
| 4 Sept – 10 Sept | ×2.3 | 11.5 % | 12/26 | 24.9 °C | 12.8 h |
| 11 Sept – 17 Sept | ×1.4 | 6.9 % | 5/26 | 24.7 °C | 12.5 h |
The meltemi has two walls, and the second one surprises
A day counts as hard above 24.3 knots sustained. The meltemi is not violent: across 26 summers the highest peak recorded is 31 knots. It is long. What strands a crew is not a gust, it is four days running at 24 hours a day above 22 knots.
Two slots concentrate these episodes: 17-23 July, thirteen blocked days across five different summers, and 14-20 August, ten days across four summers. Between them, the week of 31 July to 6 August has zero sustained episodes in twenty-six years. It is a narrow corridor, but it exists.
A colder sea than elsewhere, and the meltemi is what cools it
This is rarely mentioned: in mid-August the Cyclades sea sits at 25.6 °C against 27.7 °C in the Balearics. Two degrees less, at comparable latitude. The meltemi pushes surface water away and draws colder water up — the same wind that makes you wait is the one that makes the swimming sharper.
That cooler sea has a pleasant flip side: the nights are breathable, which is not always true in August in the western basin.
September is shifting, and it can be measured
The first late-summer blow has moved from 24 August over 2000-2012 to 2 September over 2013-2025 — nine days later. It is the only statistically clear shift we found across ten Mediterranean areas; everywhere else the risk calendar does not move.
The practical consequence: the last week of August has become more reliable than it used to be, and the first week of September less so. It remains the worst week of the Cycladic calendar, at two and a half times the norm.
How these figures are produced
Hourly ERA5 reanalysis over 26 summers (2000-2025) at an open-sea point, calibrated against stations that actually measure — the AEMET, Météo-France and NOAA networks. The “hard day” threshold is the local 95th percentile, never a shared value: 24.3 knots here. The comparison is made on ranks, not on knots, because the gap between measured and modelled gusts ranges from half a knot to thirty-one depending on the coast.
One caveat, because it matters: this index measures frequency, not severity. A week rated very calm can still hold the worst day of the decade.
Frequently asked questions
Does the meltemi blow all summer in the Cyclades?
No. Across 26 summers there are 18 sustained episodes of three days or more, concentrated in July and August. Between 15 May and 11 June, none at all.
Can you sail the Cyclades in August?
Yes, provided you pick the week. 31 July to 6 August shows no sustained episode over 26 years; 14-20 August is one of the two walls of the season. One week apart changes everything.
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