The Athens metropolitan area (Greek: Μητροπολιτική Περιοχή της Αθήνας) spans 2,928.717 km² (1,131 sq mi) within the Attica region and consists of 58 municipalities plus areas of East Attica and West Attica, having reached a population of 3,638,281 according to the 2021 census.^[2] Municipalities of Athens and Piraeus both serve as the two metropolitan centres of the Athens metropolitan area.^[3]

According to the Hellenic Telecommunications and Post Commission, the Athens metropolitan area consists of all areas with a dialing code of 21 and includes areas such as Salamina, Elefsina, Kifissia, Mandra, Aspropyrgos, Pallini, Agios Stefanos, Dionysos, Koropi, Vari, Vouliagmeni, Voula, Dafni, Chalandri and the Athens International Airport.^[4][5][6][7]

The Athens Urban Area, also known as Greater Athens,^[8] consists of 40 municipalities, 35 of which make up what was referred to as the former Athens Prefecture municipalities, located within 4 regional units (North Athens, West Athens, Central Athens, South Athens); and a further 5 municipalities, which make up the former Piraeus Prefecture municipalities, located within the regional unit of Piraeus. The Athens Municipality forms the core and centre of Greater Athens, which in turn consists of the Athens Municipality and 40 more municipalities, divided in four regional units, accounting for 2,611,713 people (in 2021) within an area of 361 km² (139 sq mi). The regional units of Central, North, South, and West Athens, Piraeus and parts of East ^[9] and West Attica^[10] regional units combined make up the continuous Athens Urban Area. ^[10][11][12]

Due to its large area metropolitan Athens has a variety of climates. The largest part of the Athens metropolitan area has a hot-summer Mediterranean climate (Köppen climate classification: Csa), while some areas of the Athens Riviera, some areas of the Thriasio Plain and some areas in the west have a hot semi-arid climate (Köppen climate classification: BSh). According to the meteorological stations of the National Observatory of Athens and the Hellenic National Meteorological Service areas in the north have wetter and colder winters. Dionysos has a January average high of around 9°C and an average low of 4°C, while Parnitha mountain has a January average high of around 4°C and an average low below 0°C. ^{[13][14] [15]} Areas in the south have very mild winters with Nea Smyrni recording a January average high of around 15°C and an average low of around 9°C. ^{[13] [16]}

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 of around 35°C. ^{[17] [13] [18]} 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. ^{[13] [19]} The highest average annual temperatures are recorded in Nea Smyrni registering around 20.4°C, while the lowest is recorded in Parnitha mountain with less than 11.0°C. ^{[13] [20] [21]} Neos Kosmos is the warmest area of Downtown Athens with an average annual temperature of 20.1°C.

The lowest average annual precipitation is recorded in Piraeus and the Athens Marina with around 315 mm to 330 mm, while the highest average annual precipitation is recorded in Parnitha mountain with around 720 mm. ^{[13] [22] [23] [24]} The highest temperature ever recorded in the Athens metropolitan area was 48.0°C in Elefsina and Tatoi on July 10, 1977 which according to the World Meteorological Organization was also the highest official temperature ever recorded in Europe until 2021.^[25] The lowest temperature ever recorded was -12.0°C in Parnitha mountain on January 9, 2017. ^[26] Furthermore, Metropolitan Athens has experienced temperatures of 47.5°C and over in four different locations.

Regarding the whole of the Attica peninsula, the lowest average annual precipitation is found in Anavysos, Athens Riviera with around 310 mm, while the highest average annual precipitation is found in Ippokrateios Politeia with over 870 mm. ^{[13] [27] [28]} Lavrio is the only area in Attica that has never recorded an air frost according to the National Observatory of Athens station which operates since 2008. ^{[29] [13]}