The Apennine chain too, confronting the wet winds from the Tyrrhenian, causes considerable climatic differences between the opposite sides of the peninsula. The differences in temperature between the winter and summer months are more marked in the northern regions than in the south and along the coasts. The mean temperatures for the month of January in the Po Plain fluctuate around zero, while in the Alpine valleys the thermometer can drop to -20º and snow can remain on the ground for many weeks.
In the southern regions, instead, the mean temperatures for January remain around 10º, with the exception of the inland mountainous zones. Mean summer temperatures throughout all Italy rise to 24º-25º for July, only being lower in the highest zones. Rainfall distribution also varies considerably, due to the influence of both mountains and prevailing winds. The highest quantities are registered in the Alpine arc (over 3,000 mm pa in the Lepontine and Julian Alps) and on the Apennines (over 3,000 mm pa in the Apuan Alps). The plains, however, including that of the Po, receive scarce precipitation. Generally it is less than 800-900 mm pa but in the southern regions (Tavoliere and southern Sicily) it falls below 600 mm pa. The great internal Alpine valleys and the coastal plains of the Tyrrhenian (Maremma) and Sardinia also receive little rain. Altogether, six large climatic regions can be distinguished, mainly characterized by mountain influence.
1) An Alpine region, strongly influenced by altitude, with long cold winters and short cool summers having an elevated day-time temperature range; precipitation is more intense in the summer months, especially in the pre-Alpine belt.
2) A Po region, with continental conditions, consisting of cold and often snowy winters and warm and sultry summers; precipitation is greatest in the spring and autumn months; the climate becomes milder, however, around the pre-Alpine lakes; fog is frequent, due to the wetness of the land.
3) An Adriatic region, whose sea has little influence due to the inability of its shallow waters to trap the summer heat; consequently the climate has a continental character, with its winters being dominated by cold north-east winds (bora).
4) An Apennine region, also with continental tendencies and cold snowy winters; precipitation is more intense on the Tyrrhenian slopes and is abundant in all seasons apart from the summer.
5) A Ligurian-Tyrrhenian region, with a maritime climate and heavy and frequent precipitation, which is less in the summer and distributed irregularly; the winters are cool and the annual temperature range narrow.
6) A Mediterranean region, also with a limited annual temperature range; precipitation is frequent, especially in winter, and the summers are hot and dry. The interior and mountain zones of the islands and Calabria also have an Apennine type climate due to the altitude.
Courtesy of the Italy Tourism Board
