Greece, although small in size, has a very diverse climate.
The majority of the country, which includes all coastal areas, has a so-called Mediterranean climate, which is nearly the same as most parts of California. Summers are hot and dry with a period of 7 months of almost constant sunshine, usually from April to November. The rest of the year is characterized by a relatively cold and rainy period that usually begins in November and lasts until late March or early April. Sporadic rainfall occurs during the dry season, but it is usually brief and infrequent. The Ionian coast and islands generally receive more annual rainfall than the rest of the country. The islands in the southern Aegean Sea and parts of the south-eastern mainland are the driest areas of the country.
The most pleasant weather is in May-June and September-October. The hottest period of the year begins in mid-July and usually lasts until mid-August, when the annual Meltemia winds from the north cool the land. The period from mid-July to mid-August is the height of summer, and the midday sun tends to be very strong; during this period, most Greeks avoid intense outdoor physical activity between 1 and 5 pm. It is best to adapt to the lifestyle of the locals by getting up early, doing all your sightseeing and shopping in the cool morning hours and then spending the afternoon in the shade or on the beach. In fact, the majority of tourists come to Greece at the height of summer to do this! For visitors from more northern climes, the low season, from November to February, can be a rewarding time to visit Greece. It won’t be beach weather, but the temperatures will be mild. The big advantage is that there are very few other tourists and prices are reduced.
Summer evenings tend to be very rewarding. As strong as the sun may shine on a summer afternoon, the low humidity in most parts of the country prevents the air from retaining much heat, and temperatures tend to drop to very comfortable levels in the evenings. But even at noon, the high temperatures are actually quite pleasant, as long as you don’t spend your time running or doing other physical activity. (However, Athens can be uncomfortably hot on summer afternoons, as the city is mostly concrete, an effect similar to that of New York). Coastal areas close to open water (away from bays and narrow gulfs), especially on many islands, tend to be quite windy and can be quite cold at night.
While the Mediterranean climate dominates most of the country, there are two other climate systems. One is the cool Alpine climate, which is found in the mountainous inland areas, including many high-altitude valleys. Another system is the continental climate, found in the interior of north-central and north-eastern Greece, which gives these regions very cold winters and hot, relatively humid summers.