Late May through early July and all of September are the sweet spots: swimming-ready seas, open ferries, and manageable cruise-ship volume on Santorini. August is hot, windy on some Cyclades, and fully booked — avoid unless you love peak energy.
Shoulder seasons shine differently. April and October bring wildflowers, hiking weather on Crete and Naxos, and hotel deals. Many beach bars on smaller islands close by mid-October; confirm ferry schedules if island-hopping late season.
Each archipelago has micro-climates. Ionian islands (Corfu, Kefalonia) green up earlier; Dodecanese (Rhodes, Kos) extend warmth into October.
Athens (ATH) plus ferry or short flights to islands is standard. SnagAFlight fare calendars help you spot cheaper mid-week hops before locking ferry tickets on direct operator sites.
