The climate of Italy is highly diverse. In most of the inland northern and central regions, the climate ranges from humid subtropical to humid continental and oceanic. The climate of the Po Valley geographical region is mostly humid subtropical, with cool winters and hot summers.Adriana Rigutti, Meteorologia, Giunti, p. 95, 2009.Thomas A. Blair, Climatology: General and Regional, Prentice Hall pp. 131–132 The coastal areas of Liguria, perience a Mediterranean climate according to the Köppen climate classification.
Between the north and south, there can be a considerable difference in temperature, especially during in winter: on some winter days, it can be and snowing in Milan, while it is in Rome and in Palermo. Temperature differences are less extreme in the summer. On 11 August 2021, an agricultural monitoring station near Syracuse recorded which constitutes the official record for the highest temperature in Europe according to the World Meteorological Organization.
Italy is experiencing widespread impacts of climate change, with an increase in extreme events such as thunderstorms heatwaves, droughts and more frequent flooding. For example, Venice is facing increasing issues due to sea level rise. Italy faces many challenges adapting to climate change including the economic, social, and environmental impacts that climate change creates, as well as an increasingly problematic death toll from the health risks that come with climate change.
Generality
The Italian climate is influenced by the Mediterranean Sea, a large body of water that surrounds Italy on every side except the north. This sea constitutes a reservoir of heat and humidity for Italy. 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.
In addition to Mediterranean influences, the Italian climate is partly affected by the western currents, especially in the intermediate seasons, as well as by the dynamics in the Atlantic Ocean, with its cyclones that travel from west by the reciprocal position, on a synoptic level, of the Azores anticyclone and the . The cold winter air are in part influenced by the mountain ranges of the Alps and the Apennines. The mitigating effect of the Mediterranean is added to this condition, with a tendency to reinvigorate, due to the transfer of sensible heat and humidity, the weakened perturbations from the west or with the formation of or Mediterranean cyclogenesis.
Geography
Italy is located in southern Europe and it is also considered a part of western Europe between latitudes 35° and 47° N, and longitudes 6° and 19° E. To the north, Italy borders Switzerland, France, Austria and Slovenia and is roughly delimited by the Alpine watershed, enclosing the Po Valley and the Venetian Plain. To the south, it consists of the entirety of the Italian Peninsula, crossed by the Apennines, and the two Mediterranean islands of Sicily and Sardinia, in addition to many smaller islands. The sovereign states of San Marino and Vatican City are enclaves within Italy, while Campione d'Italia is an Italian exclave in Switzerland.
Italy is part of the Northern Hemisphere. The country's total area is , of which is land and is water. Including islands, Italy has a coastline of on the Adriatic Sea, Ionian Sea, Tyrrhenian Sea, Ligurian Sea, Sea of Sardinia and Strait of Sicily, and borders shared with France (), Austria (), Slovenia () and Switzerland (). San Marino () and Vatican City (), both enclaves, account for the remainder.
Over 35% of the Italian territory is mountainous. The Apennine Mountains form the peninsula's backbone, and the Alps form most of its northern boundary, where Italy's highest point is located on Mont Blanc summit (Monte Bianco) (). Other worldwide-known mountains in Italy include the Matterhorn (Monte Cervino), Monte Rosa, Gran Paradiso in the West Alps, and Bernina, Stelvio and Dolomites along the eastern side. The Po, Italy's longest river (), flows from the Alps on the western border with France and crosses the Po Valley on its way to the Adriatic Sea. The Po Valley is the largest plain in Italy, with , and it represents over 70% of the total plain area in the country.
Description Conditions on the coast are different from those in the interior, particularly during the winter months when the higher altitudes tend to be cold, wet, and often snowy. The coastal regions have mild winters and warm, and generally dry summers, although lowland valleys can be quite hot in summer. Average winter temperatures vary from in the Alps to in Sicily, so average summer temperatures range from to over . 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.
The east coast of the Italian Peninsula is not as wet as the west coast but is usually colder in the winter. The east coast north of Pescara is occasionally affected by the cold bora winds in winter and spring, but the wind is less strong here than around Trieste. 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 at an elevation can often see of fresh snow fall in 24 hours during these episodes.
On the coast from Ravenna to Venice and Trieste, snow falls more rarely. During cold spells from the east, the cold wind can be harsh but with bright skies. 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 inland, and sometimes the coast from Venice to Jesolo sees snow while it is raining in Trieste and its surroundings, the Po River mouths and Ravenna. Rarely, the city of Trieste has experienced snow blizzards with north-eastern winds. In the colder winters, the Venice Lagoon may freeze, and in the coldest ones,it may even fareez enough to walk on the ice sheet (December 1788). Further south, snow may occur inland but it rarely happens at sea level, though snow at sea level has been recorded as far south as Sicily. Winters are generally milder in the coastal areas of the south, Sicily and Sardinia.
Summer is usually more stable, although the northern regions often have thunderstorms in the afternoon and night hours and some grey and rainy days. So, while south of Florence, the summer is typically dry and sunny; in the north, it tends to be more humid and cloudy. The humidity can make the northern plains particularly uncomfortable.
Spring and autumn weather can be very changeable, with sunny and warm weeks (sometimes with summer-like temperatures) suddenly interrupted by cold spells or followed by rainy and cloudy weeks.
Sunshine duration, solar irradiance and cloud cover
Based on the maps of sunshine durationAtlante Geografico Metodico De Agostini, 2002, Novara, Istituto Geografico De Agostini, p. 85.M. Pinna, L'eliofania in Italia, Roma, 1985, (Memorie della Società Geografica Italiana, 39), pp. 23-58. and on global solar irradianceLavagnini A., Martorelli S., Coretti C. (1987). Radiazione solare in Italia. Mappe mensili della radiazione globale giornaliera. Roma, CNR, Ist. Fis. Atm. in Italy, the areas with the highest values are the coasts of Sardinia, the western and southern coastal strip of Sicily, the whole of Apulia, south of Bari, and the coastal strips of the southern Tuscan Archipelago. All these areas have values of more than 2,600 hours of sunshine per year, with an average of more than seven hours per day.
On average, the northern and eastern coastal strip of Sicily, the innermost areas of Sardinia, the entire western peninsular coast to the south of Livorno, including the flat and hilly areas of the hinterland, the Ionian coast between Calabria and Basilicata, the inland areas of Lucania, the Adriatic coasts of Molise and the whole of northern Apulia, receive between 2,400 and 2,600 hours of sunshine per year (between 6.5 and seven hours per day).
Values between 2,200 and 2,400 hours of sunshine per year (between 6 and 6.5 hours per day) are recorded in the innermost areas of Sicily, in some sections of the Calabrian Ionian coast, and in the corresponding inland areas, along the Adriatic coast of Abruzzo, in Liguria, Versilia, the inland areas of northern and eastern Tuscany, in Umbria and in the hinterland of southern Lazio and Campania. All the other areas north of the imaginary oblique transversal line, drawn between the area immediately north of the city of Genoa and the border between Marche and Abruzzo, record annual average values that do not reach 2,200 hours or less than six hours per day.
The highest annual average values in the network of pyranometric stations relating to global solar irradiance are higher than and pertain to the southern and southeastern extremities of Sicily. Average annual values between and are recorded over a large part of the Aosta Valley, on the western alpine extremity of Piedmont, on the island of Pianosa, and in the coastal and sublittoral areas of the central and southern Lazio, in the south-central Apulia, Calabria, Sardinia and most of Sicily (including the islands of Ustica, Pantelleria and Lampedusa).
Average annual values between and affect western Liguria, a large part of Tuscany, and central-northern Lazio, a large part of the Marche, Abruzzo and Molise, Campania, Basilicata, northern Puglia and northeastern Sardinia. Average annual values between and occur in central-eastern Piedmont, eastern Liguria, Lombardy, Trentino-Alto Adige, Veneto, Friuli-Venezia Giulia, most of Emilia-Romagna and on the Apennine ridge between Emilia, Tuscany, Umbria, Marche and Lazio. Average annual values of less than are recorded in an area of the Tuscan-Emilian Apennines, which includes the highest peaks.
Cloud cover generally tends to reach the lowest average values in the month of July, while the highest average values, according to the different climatic zones, can occur several months between late autumn and the early part of spring, with the highest average values recorded in the most of the territory in November.
Precipitation
In the south, summer marks a distinct dry season, characteristic of Mediterranean climates. This includes cities such as Naples, Rome, Bari, and Palermo. In the north, precipitation is more evenly distributed throughout the year, although the summer is usually slightly wetter. Between November and March, the Po Valley is often covered by fog, especially in the central zone (Pavia, Piacenza, Cremona, and Mantua), while the number of days with lows below is usually from between 60 and 90 a year, with peaks of 100–110 days in the mainly rural zones.
Snow is quite common between early December and early March in cities like Turin, Milan, and Bologna, but sometimes it appears in late November or late March and even April. In the winter of 2005–2006, Milan received around or of fresh snow, Como around or , Brescia or , Trento or , Vicenza around or , Bologna around or , and Piacenza around or .
Often, the largest snowfalls happen in February, sometime in January or March. In the Alps, snowfalls more in autumn and spring over , because winter is usually marked by cold and dry periods; while the Apennines see many more snow falls during winter, but they are warmer and less wet in the other seasons.
Both mountain chains can see up to or of snow in a year at . On the highest peaks of the Alps, snow may fall even during mid summer, and glaciers are present.
Temperatures