Guide · When to go

Skiathos sea temperature and the months to swim

No official body publishes a month-by-month sea temperature around Skiathos. What the records do give is when the Aegean turns warm, how hot the air gets, how long the days last and when the north wind blows.

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Editorial team, skiathosboattrip.comUpdated October 20, 2026about 6 min to read9 sources

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Quick answer

01Sea data: No official monthly series for Skiathos; the nearest study covers the whole Aegean.¹
02Warm sea starts: Between April 28 and May 21, from Navy records of 1965 to 1995.¹
03Warm sea ends: Between October 27 and November 19.¹
04Hottest air: July, with average highs of 31.6 °C.²
05Windy month: August brings the meltemi, very strong north winds.³

What is known about the sea around the island

The sea temperature around Skiathos is the number every swimmer wants, and it is the one no official body publishes for the island month by month. No public agency record found for this page gives a monthly sea series for the island, so treat any exact figure you see quoted with caution unless it names a station. It is better to know the season than to trust a single number.

What does exist is a study of the Aegean as a whole. Researchers used records from 8 stations of the Hellenic Navy Hydrographic Service, covering 1965 to 1995, and found that the warm period of the sea surface begins between April 28 and May 21 and ends between October 27 and November 19.¹ The study gives no figure for Skiathos itself, so read the dates as a guide for the region, not a measurement at the harbor.¹

For planning, that window is useful enough. It says the sea warms in late spring, stays warm through the summer and keeps its warmth into autumn. It also suggests that the best time to visit Skiathos for swimming from a boat runs from late May into October, when both the sea and the air are on your side.

The swimming year

From the first warm water to the last

Late April to May

Sea turns warm

The warm period begins between April 28 and May 21.¹
June

Long days

Daylight of 14.9 hours at mid-month.²
July

Peak heat

Average highs of 31.6 °C.²
August

Meltemi

Very strong north winds over the park area.³
Late Oct to Nov

Sea cools

The warm period ends between October 27 and November 19.¹

Air temperatures through the year

NOAA has no station on Skiathos, so the climate figures on this page come from the nearest stations it has, averaged over 1991 to 2020: temperatures from Nea Anchialos on the mainland and rainfall from the island of Skyros.² Treat them as a close regional picture rather than readings from the island itself.

In that record May brings average highs of 24 °C, June 29.7 °C, and July and August peak at 31.6 °C and 31.3 °C.² September still averages 27.3 °C by day, and October 22.6 °C.² Nights are mild in summer, with average lows of 19.5 °C in July.²

The management body of the National Marine Park describes the climate of its area, just east of Skiathos, as Mediterranean, with a rainy winter and a dry summer.⁴ It gives a mean annual temperature of 17 °C and mean annual rainfall of 515 mm for the park.⁴ Those figures match what you feel on a summer boat day: heat, light and very little rain.

Month by month

Daylight and rainy days through the year

Hours without sunDays with precipitationSeason

Per month: the hours the sun stays below the horizon in mid-month, and the days on which rain reaches 2.5 mm. NOAA, Nea Anchialos + Skyros, 1991 to 2020.²

Climate table

Highs, lows and rain by month

Month	Daylight (h)	Darkness (h)	High / low	Wet days	Warm-sea period
Jan	9.7	14.3	12 / 3 °C	6
Feb	10.7	13.3	12 / 3 °C	5
Mar	11.9	12.1	15 / 5 °C	6
Apr	13.2	10.8	19 / 8 °C	3
May	14.3	9.7	24 / 13 °C	1	warm sea
Jun	14.9	9.1	30 / 18 °C	0	warm sea
Jul	14.7	9.3	32 / 20 °C	1	warm sea
Aug	13.7	10.3	31 / 19 °C	1	warm sea
Sep	12.5	11.5	27 / 16 °C	2	warm sea
Oct	11.2	12.8	23 / 13 °C	2	warm sea
Nov	10.1	13.9	17 / 9 °C	5
Dec	9.4	14.6	12 / 5 °C	9

Sunrise-to-sunset hours in mid-month, average daily highs and lows, and rainy days counted from 2.5 mm upward. NOAA, 1991 to 2020.² Season according to Mediterranean Marine Science (2004).¹

Season by season

Early, high and late season on the water

Fresh and long

Early season

May and June

May high: 24 °C
June high: 29.7 °C
June daylight: 14.9 hrs

Plan your day

Hottest

High summer

July and August

July high: 31.6 °C
August high: 31.3 °C
August wind: Meltemi

Plan your day

Warm sea, shorter days

Late season

September and October

September high: 27.3 °C
October high: 22.6 °C
October daylight: 11.2 hrs

Plan your day

Decision helper

Which month suits your boat day?

Match the month to what matters most

The longest days on the water The warmest swim The best chance of a calm north coast Warm sea without peak heat Very little rain

June

Daylight of 14.9 hours at mid-month.²

July or August

Deep inside the warm period of the sea.¹

Avoid August

The meltemi blows in August.³

September

Average highs of 27.3 °C.²

June to August

June has 6 mm of precipitation in the month.²

The results showed that the warm period starts sometime between April 28th and May 21st while it ends between October 27th and November 19th in accordance with the findings of other studies.

Mediterranean Marine Science (Hellenic Centre for Marine Research)Source 1

Rain and daylight, month by month

Summer is close to dry. In the regional record June has 6 mm of precipitation in the month and no day with at least 2.5 mm, while July and August each average one such day.² Rain returns in autumn: November averages 73 mm and December 121 mm.²

Daylight shapes a boat trip as much as heat does. Sunrise to sunset lasts 14.9 hours in the middle of June and 14.7 hours in the middle of July.² By mid-October that falls to 11.2 hours.² A long day on the water fits easily into midsummer and becomes tighter as the season ends.

These are daylight figures, the time the sun spends above the horizon, not hours of direct sunshine. On a clear summer day the two are close; on a hazy or cloudy day they are not. For an evening cruise, check the sunset time for your date rather than relying on a monthly average, and remember that the light fades quickly at sea once the sun has gone down.

Checklist

Pack for the season you pick

Every month

Sun cream, sunglasses and a hat
Swimwear and a towel
A trip you can cancel if the wind rises

Early and late season

A light top for the crossing
Check sunset time for your date

High summer

Plenty of water on deck
Shoulders covered in the midday sun

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The north wind and the calm coves

Wind matters more than temperature for most boat days. The marine park's management body notes that in August the meltemi, very strong north winds, blow over its area.³ On Skiathos, the municipality describes the northern beaches as wild, with waves that suit windsurfing, and the southern ones as calm.⁵

That split decides where boats can go. Lalaria on the north coast can be reached only by sea, and only in dead calm, on the daily boats from the port.⁶ Kastro beach, also on the north side, is exposed to the wind and usually has waves.⁷ At Aselinos a north wind brings big waves.⁸

Day cruises plan around it. The Mamma Mia beach cruise warns that its route and stops can change in rough seas or high winds. The cruise to Lalaria, Kastro and Tsougria carries the same warning. If a north-coast beach is the reason for your trip, book early in your stay and keep a spare day in case the captain turns south.

Early season: May and June

Between late April and May 21 the Aegean crosses into its warm period, according to the Navy records.¹ The air is already pleasant, with average highs of 24 °C in May and almost no rain in June.² Days are long, and the sea feels fresh at the first swim of the morning.

This is a fine time for long days with two island stops. The day boat to Skopelos and Alonissos spends 1.5 hours on each island and adds 1 hour of swimming before the drop-off. With daylight of 14.3 hours in mid-May and 14.9 hours in mid-June, there is room for a late dinner after the boat returns.²

Pack a light top for the morning crossing and for the ride home, since the air moves fast across an open deck and spray can reach the front rows when the boat picks up speed. Bring sun cream all the same. A cooler breeze makes it easy to forget how strong the spring sun is on the water.

High summer: July and August

July is the hottest month in the regional record, with average highs of 31.6 °C, and August follows at 31.3 °C.² The sea is well inside its warm period, so swim stops feel long and easy, and a dip from the boat becomes the best part of the afternoon.¹

August also brings the meltemi.³ On a strong wind day the north coast may be off the plan, and smaller boats feel every wave. If you are prone to seasickness, a larger day boat on a sheltered southern route is the gentler choice, and a seat near the middle of the deck moves least.

Heat is the other thing to manage. Take a hat, plenty of water and something to cover your shoulders on deck. On the day boat to Skopelos and Alonissos, food and drinks are not included, so plan lunch ashore on the second island. A shaded table near the quay, a cold drink and an unhurried meal make the hottest hours of the day the easiest ones.

Late season: September and October

September keeps much of the summer: average highs of 27.3 °C with rain of 2.5 mm or more on only 2 days.² October cools to 22.6 °C by day.² The sea, by the Navy records, stays in its warm period until somewhere between October 27 and November 19.¹

Daylight shortens as you go: 12.5 hours in mid-September and 11.2 in mid-October.² A 9-hour day boat still fits, but you return closer to dusk. Evening beaches such as Agia Eleni, where the sun shines until very late in the afternoon, are a good way to end a late-season day.⁹

Whatever month you choose, book a trip you can cancel. The day boat to Skopelos and Alonissos costs nothing to cancel until a day ahead, and you can hold seats now and pay closer to the date. If the forecast turns, you can move your day without losing the fare.

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You ask,we answer.

How warm is the sea around Skiathos?

No official monthly figure exists. A study of 8 Aegean Navy stations from 1965 to 1995 dates the warm period from late April or May to late October or November.¹

When does the sea warm up?

Between April 28 and May 21. That is the Aegean-wide range from the Navy records.¹

When does it cool down?

Between October 27 and November 19. The same study dates the end of the warm period.¹

Which month is hottest?

July. Average highs reach 31.6 °C in the regional record.²

Is August windy?

It can be. The marine park notes the meltemi, very strong north winds, in August.³

Can I always reach Lalaria by boat?

No. Lalaria can be reached only by sea and only in dead calm.⁶

Where do the climate figures come from?

NOAA, two stations. A combined record from Nea Anchialos and Skyros, averaged over 1991 to 2020.²