The warmth of the ocean in Mykonos depends heavily on the month you visit, as the Aegean Sea is generally cooler than the southern Mediterranean. In 2026, the water temperature only reaches a "warm" high-fidelity state of 24°C to 26°C (75°F–79°F) from July through September. During the early season in May and June, the water is a crisp 19°C to 22°C, which many find refreshing but a bit chilly for long swims. By October, the water begins to cool down but often stays around 21°C due to the summer’s residual heat. It is also important to note the Meltemi winds—strong northern winds that blow across the Cyclades in July and August. These winds can create a "wind-chill" effect on the surface and churn up the water, making it feel cooler than the actual thermometer reading. For the warmest, calmest swimming experience, the southern beaches of Mykonos (like Psarou or Platis Gialos) are preferred as they are protected from these winds, allowing the shallow coastal waters to soak up more of the intense Greek sun.