Map from Google - Skiathos

The climate of Skiathos, Greek island of the Northern Sporades, is transitional mediterranean, with relatively cold and rainy winters, and hot and sunny summers. The average temperature of January is 6 °C (43 °F), that of July and August is 23.5 °C (74.5 °F). Being at a short distance from the mainland, the island in winter is subject to outbreaks of cold air, while in late spring and summer it may occasionally receive some showers or thunderstorms coming from the same continent.
Here are the average temperatures.
Average temperatures - Skiathos
SkiathosJanFebMarAprMayJunJulAugSepOctNovDec
SkiathosJFMAMJJASOND
Min (°C)234711161818141184
Max (°C)91113182327292926201612
Min (°F)363739455261646457524639
Max (°F)485255647381848479686154

The island's interior is covered with hills, which reach about 400 metres (1,300 feet) above sea level, and is green. The island's airport is located at a short distance from the main city, and the track is near the sea and the harbor.

Skiathos, aeroplane landing

The rains follow the Mediterranean pattern, so they are more frequent from October to April, and are not abundant, since they amount to 630 millimetres (24.8 inches) per year. As mentioned, in summer rainfall is rare, and occurs in the form of short showers or thunderstorms.
Here is the average precipitation.
Average precipitation - Skiathos
SkiathosJanFebMarAprMayJunJulAugSepOctNovDecYear
SkiathosJFMAMJJASONDY
Prec. (mm)807060404025202540706595630
Prec. (in)3.12.82.41.61.610.811.62.82.63.724.8
Days10987642257101282

Winter, from December to mid-March, is pretty cold: the maximum temperature is on average about 10/12 °C (50/54 °F), but there may be mild periods, with highs around 15/18 °C (59/64 °F), and cold periods, when highs remain at 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 at night there may be frosts. The rains are quite frequent; the rainiest month is December.

Spring, from mid-March to May, is mild, but 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 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 even in October.

The amount of sunshine in Skiathos is very good in summer, when clear skies prevail, and it is good also in May and September, while in the rest of the year it is not so high, since there are several periods in which the sky is cloudy.

Skiathos town

The temperature of the sea, still cold in May (20 °C or 68 °F), and cool in June (21 °C or 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.
Sea temperature - Skiathos
SkiathosJanFebMarAprMayJunJulAugSepOctNovDec
SkiathosJFMAMJJASOND
Sea (°C)141414151721242423211815
Sea (°F)575757596370757573706459

When to go

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

Back to the Sporades Islands.