The high season in Mykonos runs from July through August. This is when it’s most crowded, but also when it’s the most fun if you’re looking for long, sunny days and that bumpin’ party atmosphere.
However, if you enjoy a bit of peace and quiet and want to see lower prices, travel in May, June, September, or October. Unlike mainland Greece, where winter is a good time for prices and you can still enjoy hiking and tourism, a winter trip to Mykonos is probably a waste.