Climate of Italy

The climate of the Po valley geographical region is mostly humid subtropical, with cool winters and hot summers.

[6][7] The Italian climate is influenced by the large body of water of the Mediterranean Seas that surrounds Italy on every side except the north.

Within the southern temperate zone, they determine a Mediterranean climate with local differences due to the geomorphology of the territory, which tends to make its mitigating effects felt, especially in high pressure conditions.

[8] In addition to Mediterranean influences, the Italian climate is partly affected by the western currents, especially in the intermediate seasons, also by the dynamics in the Atlantic Ocean, with its cyclones that travel from west to east, driven by the zonal circulation and more generally by the reciprocal position, on a synoptic level, of the Azores anticyclone and the African subtropical anticyclone [it].

The sovereign states of San Marino and the Vatican City are enclaves within Italy,[13][14] while Campione d'Italia is an Italian exclave in Switzerland.

[17] Conditions on the coast are different from those in the interior, particularly during winter months when the higher altitudes tend to be cold, wet, and often snowy.

Winters can vary widely across the country with lingering cold, foggy and snowy periods in the north and milder, sunnier conditions in the south.

Summers can be hot and humid across the country, particularly in the south while northern and central areas can experience occasional strong thunderstorms from spring to autumn.

During these frosty spells from E–NE cities like Rimini, Ancona, Pescara and the entire eastern hillside of the Apennines can be affected by true "blizzards".

The town of Fabriano, located just around 300 m (984 ft) in elevation, can often see 50–60 cm (20–24 in) of fresh snow fall in 24 hours during these episodes.

During the snowfalls that affect Northern Italy, the Adriatic coast can see a milder Sirocco wind which makes snow turn to rain.

The mild effects of this wind often disappear just a few kilometres inside the plain, and sometimes the coast from Venice to Jesolo sees snow while it is raining in Trieste and surroundings, the Po River mouths and Ravenna.

The highest annual average values in the network of pyranometric stations relating to global solar irradiance are higher than 18 MJ/m2 (0.46 kWh/sq ft) and concern the southern and south-eastern extremities of Sicily.

Average annual values between 16 MJ/m2 (0.41 kWh/sq ft) and 18 MJ/m2 (0.46 kWh/sq ft) are recorded over a large part of the Aosta Valley, on the western alpine extremity of Piedmont, on the island of Pianosa, on the coastal and sublittoral areas of the middle and southern Lazio, in the south-central Apulia, Calabria, Sardinia and most of Sicily (including the islands of Ustica, Pantelleria and Lampedusa).

The coldest month is January: the Po valley's mean temperature is between −1–1 °C (30.2–33.8 °F), Venice 2–3 °C (35.6–37.4 °F), Trieste 6–7 °C (42.8–44.6 °F), Florence 5–6 °C (41.0–42.8 °F), Rome 7–8 °C (44.6–46.4 °F), Naples 9 °C (48.2 °F), and Cagliari 12 °C (53.6 °F).

Winter morning lows can occasionally reach −30 to −20 °C (−22.0 to −4.0 °F) in the Alps, −14 to −8 °C (6.8 to 17.6 °F) in the Po valley, −7 °C (19.4 °F) in Florence, −4 °C (24.8 °F) in Rome, −2 °C (28.4 °F) in Naples and 2 °C (35.6 °F) in Palermo.

In cities like Rome and Milan, strong heat islands can exist, so that inside the urban area, winters can be milder and summers more sultry.

A relatively "continental" and "four-season" version of the humid subtropical climate can be found in the Po and Adige valleys in the North, and sometimes in low inland Central and Southern Italy.

Summers are between 17 and 21 °C (62.6 and 69.8 °F) Main cities and towns: Aosta, Biella, Campobasso, L'Aquila, Cuneo, Sondrio, Amatrice, Belluno, Breno, Feltre.

Main towns: Brusson, Gressoney-Saint-Jean, Aprica, Vermiglio, Mazzin, Santo Stefano di Cadore, Asiago, Claut, Resia.

[76] The maximum snow depth was recorded in March 1951 in the Alps at the meteorological station of Lake D'Avino, in Piedmont, with a value of 1,125 cm (443 in).

[77] The maximum snowfall in 24 hours is 181 cm (71 in), recorded in the Apennines in the village of Roccacaramanico, frazione of Sant'Eufemia a Maiella (Majella massif), Abruzzo, on 15 January 1951.

[79] The maximum rainfall in 24 hours was recorded in Bolzaneto, a quarter of Genoa, Liguria, on 10 September 1970 with a value of 948 mm (37.3 in).

[3] Italy, like other parts of the globe, has been subject in the past to climate changes on a planetary scale (for example glaciations and interglacial periods, Little Ice Age).

Partial confirmation of many concerns was obtained starting from the 2010s with an acceleration of the water cycle, an increase in alluvial phenomena, and the tropicalization of the Mediterranean Sea.