Greece features a vast number of islands, between 1,200 and 6,000, depending on the definition, 227 of which are inhabited. Crete is the largest and most populous island; Euboea, separated from the mainland by the 60m-wide Euripus Strait, is the second largest, followed by Lesbos and Rhodes.
The Greek islands are traditionally grouped into the following clusters: The Argo-Saronic Islands in the Saronic gulf near Athens, the Cyclades, a large but dense collection occupying the central part of the Aegean Sea, the North Aegean islands, a loose grouping off the west coast of Turkey, the Dodecanese, another loose collection in the southeast between Crete and Turkey, the Sporades, a small tight group off the coast of northeast Euboea, and the Ionian Islands, located to the west of the mainland in the Ionian Sea.
The climate of Greece is primarily Mediterranean, featuring mild, wet winters and hot, dry summers. This climate occurs at all coastal locations, including Athens, the Cyclades, the Dodecanese, Crete, the Peloponnese, the Ionian Islands and parts of the Central Continental Greece region. The Pindus mountain range strongly affects the climate of the country, as areas to the west of the range are considerably wetter on average (due to greater exposure to south-westerly systems bringing in moisture) than the areas lying to the east of the range (due to a rain shadow effect).
The mountainous areas of Northwestern Greece (parts of Epirus, Central Greece, Thessaly, Western Macedonia) as well as in the mountainous central parts of Peloponnese – including parts of the regional units of Achaea, Arcadia and Laconia – feature an Alpine climate with heavy snowfalls. The inland parts of northern Greece, in Central Macedonia and East Macedonia and Thrace feature a temperate climate with cold, damp winters and hot, dry summers with frequent thunderstorms. Snowfalls occur every year in the mountains and northern areas, and brief snowfalls are not unknown even in low-lying southern areas, such as Athens.
Phytogeographically, Greece belongs to the Boreal Kingdom and is shared between the East Mediterranean province of the Mediterranean Region and the Illyrian province of the Circumboreal Region. According to the World Wide Fund for Nature and the European Environment Agency, the territory of Greece can be subdivided into six ecoregions: the Illyrian deciduous forests, Pindus Mountains mixed forests, Balkan mixed forests, Rhodope montane mixed forests, Aegean and Western Turkey sclerophyllous and mixed forests and Crete Mediterranean forests.