May, June, and September are the ideal months — warm enough to swim, uncrowded, and with the island's wildflowers and greenery still visible before the summer heat burns everything brown. July and August bring the meltemi wind, which is excellent for windsurfers but can make some beaches choppy and some ferry crossings uncomfortable.
Winter is quiet to the point of closure: many restaurants and boat services shut from November to April, and the northern part of the island is effectively inaccessible by public transport. The island comes back to life gradually from Easter onwards.