The climate of Skiathos, a Greek island belonging to the Northern Sporades, is transitional Mediterranean, with relatively cold, rainy winters and hot, sunny summers.
The daily average temperature ranges from 6 °C (43 °F) in January to 23.5 °C (74.5 °F) in July and August. Here are the average temperatures.
Skiathos - Average temperatures
Min (°C)234711161818141184
Max (°C)91113182327292926201612
Min (°F)363739455261646457524639
Max (°F)485255647381848479686154

Being a short distance from the mainland, the island is subject to outbreaks of cold air in winter, while in late spring and summer, it may occasionally receive some showers or thunderstorms coming from the same continent.
The island's interior is covered with hills, which reach about 400 meters (1,300 feet) above sea level, and it's green. The airport is located a short distance from the main town, and the track is a few steps away from both the sea and the harbor.

Skiathos, aeroplane landing

Rainfall follows the Mediterranean pattern, so it is more frequent from October to April, and is not abundant, since it amounts to 630 millimeters (24.8 inches) per year. As mentioned, rainfall is rare in summer, and occurs in the form of short showers or thunderstorms. Here is the average precipitation.
Skiathos - Average precipitation

Winter, from December to mid-March, is pretty cold: the maximum temperature is on average about 9/12 °C (48/54 °F), but there can be mild periods, with highs around 15/18 °C (59/64 °F), and cold periods, when highs remain around 5/7 °C (41/45 °F), and with a moderate or even strong wind that heightens the feeling of cold. In addition, sometimes, and not too infrequently, it can snow, and there may be frosts at night.
The rains are quite frequent; the rainiest month is December.

Spring, from mid-March to May, is mild, though with some periods a bit cold, windy and rainy, which gradually become less frequent.

Summer, from June to mid-September, is hot and sunny, with rare showers. Typically, the maximum temperatures hover around 30 °C (86 °F) and rarely exceed 33/34 °C (91/93 °F), but the air is a bit humid.

Autumn, from mid-September to November, is pleasantly warm at first, then gradually becomes milder. The rains gradually become more frequent, although in September and the first half of October, there are still entire weeks without rain. In November, the first days a bit cold and windy begin to occur, and sometimes also in October.

Skiathos town

The amount of sunshine in Skiathos is very good in summer, when clear skies prevail, and it is also good in May and September, while in the rest of the year, it is not so high, since there are several cloudy periods. Here are the average sunshine hours per day.
Skiathos - Sunshine

The temperature of the sea, still cold in May and cool in June, when it's around 21 °C (70 °F), becomes high enough for swimming from July to September, when it reaches 23/24 °C (73/75 °F). Here are the average sea temperatures.
Skiathos - Sea temperature
Temp (°C)141414151721242423211815
Temp (°F)575757596370757573706459

Best Time

The best time to go to Skiathos for a beach holiday is summer, from June to mid-September. In June, and sometimes in early July, there can be some cool evenings, so it's better to bring a sweatshirt for the evening.
In May, not only the sea is cold, but there can also be some cool days for sunbathing, with highs below 20 °C (68 °F), especially in the first part of the month.
If you want to go on excursions on the island, you can choose May and September.

Back to the Sporades Islands.