Greek Islands Sea Temperature by Month
Pick a destination and a month to see the typical sea temperature, how comfortable the water is for swimming and snorkelling, how the islands compare, and which catamaran cruise suits that time of year. Figures are long-term climatological averages for sea-surface temperature.
Sea temperature through the year
Average sea-surface temperature, month by month. Tap any month to update. The highlighted bar is your selection.
Compare the islands this month
Ready for the water?
A DanEri catamaran day cruise anchors at the clearest bays with lunch on board — the best way to enjoy this sea.
The sea across the Greek islands is warmest in August (about 25–28°C / 77–82°F) and comfortable for swimming from roughly late May to October. Cyprus is the warmest of these destinations and stays swimmable longest; Crete and Rhodes are close behind, and Milos (Cyclades) runs a touch cooler. The coldest water is in February (15–17°C). For warm water with thinner crowds, September is the sweet spot everywhere.
Sea temperature by island, warm season
Average sea temperature in °C, May to October. Warmer cells shade toward coral, cooler toward teal.
| Island | May | Jun | Jul | Aug | Sep | Oct |
|---|---|---|---|---|---|---|
| Cyprus | 21° | 25° | 27° | 28° | 27° | 25° |
| Crete | 20° | 23° | 25° | 26° | 25° | 23° |
| Rhodes | 20° | 23° | 25° | 26° | 25° | 23° |
| Milos | 19° | 22° | 24° | 25° | 24° | 22° |
Ranked warmest to coolest in peak season. Cyprus leads by roughly 1–2°C; the three Aegean/Cretan-sea destinations are within a degree of each other.
Each island at a glance
Warmest month, coldest month, and how long the swimming season runs — with a link to the full guide for each.
What counts as warm enough?
A rough guide to how the water feels at each temperature, so you know what to expect before you dive in.
About the data: figures are typical long-term monthly averages for sea-surface temperature and will vary year to year and within a region. Actual conditions on the day depend on wind, currents and recent weather. For sailing conditions also check the local forecast.
How we built this. Monthly figures are drawn from long-term sea-surface-temperature climatology for each region and cross-checked against what DanEri crews record at swim stops through the season. Air-temperature figures are typical daytime highs. Sea temperature is shown to the nearest degree; the “swim season” marks months averaging 21°C (70°F) or above.
Within an island, sheltered south- or east-facing coasts can run a degree or two warmer and calmer than exposed north coasts, and shallow bays warm faster than open water.
Greek islands sea temperature — common questions
When is the sea warmest in Greece?
August is the warmest month across the Greek islands, with sea-surface temperatures typically around 25–28°C (77–82°F). Cyprus runs the warmest, followed by Rhodes and Crete, then the Cyclades. September stays almost as warm and is often the sweet spot — warm sea, thinner crowds.
What months can you swim comfortably in the Greek islands?
Most swimmers are comfortable from late May to October, when the sea sits roughly 21–28°C. May is refreshing (about 19–21°C) and November is still swimmable in Cyprus and the Dodecanese (around 21–22°C). December–April is cold for swimming without a wetsuit (15–18°C).
Can you swim in the Greek islands in May or October?
Yes. By late May the sea reaches about 19–21°C — refreshing but swimmable, especially in the warmer south. October is more comfortable than people expect, around 22–25°C, because the sea is still holding summer heat; early October is a lovely swimming month.
Which Greek island has the warmest sea?
Of these destinations, Cyprus has the warmest sea — roughly 1–2°C above Crete and Rhodes in the same month, peaking near 28°C in August and staying above 20°C into November. Crete and Rhodes are next, then Milos and the Cyclades.
Is the sea warm enough for snorkelling?
Yes from late May to October. Warmer water (24°C+) lets you stay in longer without getting cold, which matters for snorkelling and cave swims. In May or late October a shorty wetsuit or rash vest extends your comfort.
How cold does the sea get in winter?
The Greek islands’ sea bottoms out in February at about 15–17°C (59–63°F), warmest in Cyprus and coolest in the Cyclades. It’s cold for swimming without a wetsuit from December through April, then warms quickly through spring.
Does sea temperature affect which cruise to choose?
It helps. In peak summer (warm sea) both day and sunset cruises are great. In the shoulder season the warm midday water makes a day cruise the better swimming choice, while a sunset cruise is more about the light and the air than the swim.