Greece's busiest period is June to August, with July and August especially crowded on popular islands such as Santorini, Mykonos, Crete and Rhodes. European summer holidays drive high demand for ferries, hotels and restaurants. Easter, particularly Greek Orthodox Easter, can also create domestic travel peaks, while September remains popular for warm weather and sea swimming. The quieter months are generally November to March, when many island businesses close or reduce services. May and October can offer a useful balance of milder weather and fewer crowds.

Greece's main seasonal natural hazards are summer wildfires and heatwaves, particularly from June to September, when hot, dry and windy conditions can allow fires to spread quickly. Earthquakes are possible year-round, as Greece is in a seismically active region. Flash flooding and severe storms are more likely during wetter months, especially autumn and winter. The peak summer travel season overlaps with wildfire risk, which can lead to evacuations, road closures and transport disruption. Check local alerts during heatwaves and follow authorities' guidance near affected areas.

Greece has a Mediterranean climate, with hot, dry summers and mild, wetter winters. June to September is generally sunny and warm, with July and August often very hot and occasionally affected by strong winds. Spring, especially April and May, brings milder temperatures and wildflowers, while September and early October often retain warm seas with less intense heat. November to March is cooler and wetter, particularly on the mainland. For sightseeing and outdoor activities, May, June and September are often comfortable alternatives to the peak summer heat.