Greece enjoys one of the finest climates in Europe, with long hot summers, mild winters, and over 300 days of sunshine per year. The best overall times to visit are May–June and September–October — when temperatures are warm but not overwhelming, the sea is swimmable, crowds are manageable, and prices are significantly lower than July–August peaks.
Spring (April–June)
Spring is arguably the finest season to visit mainland Greece and the islands. April sees wildflowers blanket the hillsides of Crete and the Peloponnese, temperatures are mild (18–24°C), and crowds are thin. The sea is cool in April but warms rapidly through May. By May and June, conditions are near-perfect across most of Greece: warm, sunny days (24–28°C), comfortable evenings, a swimmable sea (22–24°C by June), and the tourist infrastructure fully open without the summer crush. Athens is particularly pleasant in spring — ideal for sightseeing without the heat. Greek Easter (moveable, usually April or early May) is a major cultural event, with atmospheric candlelit processions and lamb roasts; some accommodation books up months in advance for Easter weekend.
Summer (July–August)
Greece in high summer is intensely popular, intensely hot (30–40°C on the mainland and many islands), and intensely busy. The meltemi wind, which blows strongly across the Aegean from July to mid-August, provides some relief from the heat on the Cyclades but can make sea crossings rough. Athens in August is brutally hot and many Athenians flee to the islands, leaving the city quieter than usual. The islands are at maximum capacity — Mykonos, Santorini, and Rhodes are particularly congested — and prices for accommodation and ferries are at their peak. The sea is gloriously warm (26–28°C), beaches are lively, and the nightlife is exceptional. Come in summer for the full Greek beach holiday experience, but book everything months in advance.
Autumn (September–October)
September is one of the best months to visit Greece. Temperatures remain hot (26–30°C), the sea is at its warmest (25–27°C), crowds have thinned significantly from August, prices are lower, and the quality of light is extraordinary. October is warm and pleasant (18–24°C) with continued excellent swimming through mid-month; autumn rains begin on the mainland and some northern islands from late October. The grape harvest is underway on Santorini and other wine islands in September — a wonderful time for food and wine tourism. Many island hotels and restaurants close from late October or November.
Winter (November–March)
Winter in Greece is mild by northern European standards (10–15°C) and often sunny, but most island tourism infrastructure closes entirely. Athens is the main destination for winter visitors — the archaeological sites are quieter than at any other time of year, accommodation prices are at their lowest, and the city's museums, restaurants, and cultural life continue uninterrupted. Thessaloniki is excellent in winter: a thriving urban destination with fine Byzantine sights, superb food, and a lively local culture. For skiing, Mount Parnassus near Delphi and resorts in northern Greece offer reasonable winter sports. The Ionian Islands, which receive more rainfall than the Aegean, are less appealing in winter.