Climate: Athens owes its good climate, mild winters and warm summers cooled by a system of seasonable winds, to its geographic position. The general condition of the weather in Athens usually stabilizes in early summer, and is characterized by bright sunshine and very little rainfall. Athens is perfect for those who enjoy the sun, as for over two thirds of the year the city basks under clear, sunny skies.
 Temperature do vary, however. Summers are long and dry, with extremes of 37o C (99o F), making the yearly mean temperature about 17o C (63o F). Winters are mild and sometimes rainy, with quite low temperatures.
 Clothing: lightweight clothes during summer months, including protection from the midday sun (hats, sunglasses etc.). light sweatshirts are needed for evenings. Rainproof jackets are advised for autumn and normal winter-wear (woolen sweatshirts, winter coat etc.) during winter.

You can find Athens weather forecast here