In addition to Athens, it contains within its area the cities of Elefsina, Megara, Laurium, and Marathon, as well as a small part of the Peloponnese peninsula and the islands of Salamis, Aegina, Angistri, Poros, Hydra, Spetses, Kythira, and Antikythera.

While being supervised by the Decentralized Administration of Attica, it is now an independent self-governing body with powers and a budget comparable to the former prefectures.

[6][9] The islands of the Attica region have even milder winters with Hydra recording a January average low of over 10°C and falling in 11a hardiness zone.

[10][11] The highest July and August temperatures are recorded in the interior of the Athens Basin and also in west areas with Nea Filadelfeia, Harokopio University and Salamina registering average summer highs over 35°C.

[12][6][13] Due to land breezes, summer nights can be particularly hot in the south and especially around Piraeus which records an average August low of around 27°C.

During July 2024 minimum temperatures remained over 30 °C (86 °F) for 12 consecutive days in metropolitan Athens, breaking all known records for any area in the country.

[19] Lavrio is the only area in mainland Attica that has never recorded an air frost according to the National Observatory of Athens station which operates since 2008.