Cyclades Islands, map

The Cyclades Islands are located in the central part of the Aegean Sea, and have a Mediterranean climate, with mild and moderately rainy winters, and warm, sunny summers. The wind blows frequently: in winter a cold wind from the continent can blow, while summers are characterized by the almost constant breath of the Meltemi, a wind that reduces the feeling of heat, but at the same time maintains a bit cool the temperature of the sea, and can also make the sea rough and create sea currents.
The main islands of the Cyclades are Amorgos, Anafi, Andros, Antiparos, Kimolos, Delos, Ios, Kea, Folegandros, Kythnos, Milos, Mykonos, Naxos, Paros, Rineia, Serifos, Sifnos, Sikinos, Syros, Tinos and Santorini.
To the south of Naxos we find the small archipelago of the Lesser Cyclades, which includes the islands of Ano Koufonisi, Kato Koufonisi, Donoussa, Schoinoussa, Irakleia and Keros (with the neighbouring small islands of Ano Antikeri and Kato Antikeri). The Lesser Cyclades have a climate similar to that of neighbouring Naxos and Ios.

The average temperatures of January and February hover around 11 °C (52 °F), those of July and August around 25 °C (77 °F).
Here are for example the average temperatures in Santorini: as you can see, daytime temperatures normally remain below 30 °C (86 °F) even in July and August. During heat waves, when in other areas of Greece the temperatures can touch 40 °C (104 °F), in the Cyclades they typically remain lower, around 34/35 °C (93/95 °F).
Average temperatures - Santorini
SantoriniJanFebMarAprMayJunJulAugSepOctNovDec
SantoriniJFMAMJJASOND
Min (°C)9910121519222219161311
Max (°C)141416192227282726221916
Min (°F)484850545966727266615552
Max (°F)575761667281828179726661

In winter, especially in January and February, the islands may be affected by outbreaks of cold air from the continent, and in these cases there may be cold days, with highs below 10 °C (50 °F), and a strong wind able to increase the feeling of cold. Sometimes it can even snow, especially in the northern islands, and in the islands equipped with hills and low mountains.

Snow in Tinos

The rains in the Cyclades are not abundant, since they are generally below 500 millimetres (20 inches) per year (and sometimes even 400 mm or 16 inches), and are concentrated in the cold period, from October to March, when they can occur in the form of showers or thunderstorms.
Because of the long summer drought, the landscape is typically semi-arid, especially in the flat islands, in the southern slopes and along the coasts; in the islands equipped with elevations, the highest areas and the slopes exposed to the north and west are generally more verdant.
Here is the average precipitation in Milos.
Average precipitation - Milos
MilosJanFebMarAprMayJunJulAugSepOctNovDecYear
MilosJFMAMJJASONDY
Prec. (mm)75504520153016456090411
Prec. (in)321.80.80.60.1000.21.82.43.516.2
Days97631000146946

The amount of sunshine in the Cyclades is great in summer, when clear skies are the norm. In winter, periods of bad weather, with cloudy skies, alternate with sunny periods.

Folegandros

The temperature of the sea in the Cyclades Islands is never very high, because the wind that blows in summer tends to keep it a bit low, however it reaches a maximum of 23/24 °C (73/75 °F) in July and August; in June it's still a bit cool, about 21 °C (70 °F). Here, for example, the temperature of the sea at Mykonos.
Sea temperature - Mykonos
MykonosJanFebMarAprMayJunJulAugSepOctNovDec
MykonosJFMAMJJASOND
Sea (°C)161515161821232323211817
Sea (°F)615959616470737373706463

When to go

The best time to go to the Cyclades Islands for seaside tourism is the summer, from June to mid-September.
It's better to bring a sweatshirt for the cool evenings, which occur mainly in June, but given the intensity of the wind, those who are sensitive to cold can feel a little cool even in July and August, and thus can equip themselves also in these months.
For hikes, spring is good, in April and May, but since usually it's not hot, you can walk round the islands also in summer.

Back to the Greek Islands.