The rainfall in Italy takes place for the most part in autumn and winter, so that this country belongs to the region of winter and autumn rains. The Apennines form a noteworthy boundary, for a line drawn from the summit of the Ligurian range through Pisa, Rome, Capua, Salerno, Metaponto, Otranto divides the area of the winter rain from that of the autumnal rain lying north and east of it. In many parts of the country it practically never rains in summer; Rome has only a few days between June and September with appreciable rainfall. In Sicily we may anticipate six rainy days at Palermo, two at Catania, two at Syracuse in the summer on an average. In Malta it never really rains from March to September, but when rain does fall in Italy it takes the form of violent downpours such as are only seen in Germany during thunderstorms, and in these more water falls in a short time than in a week's rain in Germany. In the higher parts of the mountains this downfall naturally takes the form of snow. The ranges of Upper and Middle Italy are usually white with snow from November till April. Gran Sasso keeps the snow far into the summer, and it happens in some years that it is never free from snow. In the Neapolitan range the snow melts in March, but there is often a fresh covering of snow under a spell of cold. Even the Aspromonte in Calabria, the Nebrodes in Sicily, have a wintry appearance after the beginning of April. The highest point of Etna is not quite free from snow till August, which is the best time to ascend the mountain.
The rainfall at Milan is tolerably uniform, with a slight increase in the autumn. The dampness of the region shows itself in the fogs which occur frequently in the autumn, and are nearly as thick as in London. In Florence and Rome there is nearly the same amount of rain in autumn and winter, while the rain in summer is unimportant, the percentage in Rome being somewhat less than in Northern Tuscany, and we may lay down the rule that with the diminution of the winter rainfall from south to north that of autumn and spring increases. The country at the foot of the Alps has more plentiful rain in the early summer (May and June) and in the middle of autumn (October). The rainfall here is very large, everywhere exceeding 40 inches and reaching 5 feet at Lakes Como and Lugano, while it remains below 40 inches in the plain of the Po. The figure for Tolmezzo, is unusually large (95.8 inches), while that for Lecce is very small (21.7), reminding us of the state of things in Sicily. Apulia and Terra d' Otranto do in fact suffer from dryness, the ground in summer being parched and cracked and covered with thick dust, which the wind carries over the plain in vast clouds. The influence of the moist winds of the Tyrrhenian Sea may be recognized in the comparison of the figures for Florence (42.3 inches), Leghorn (34.6), Genoa (49.8), on one side; with Bologna (21.1), Modena (25.2), and Alessandria (26.4) on the other, which brings out the increased condensation on the southern slope of the Apennines.
The high range of mountains in Calabria acts in the same way, and procures for Cosenza (43.3), a rainfall such as is not found elsewhere except at the foot of the Alps. Denza distributes Italy into the following zones in regard to rainfall: The Alpine (68.1 inches), the sub-Alpine (36.6), the West Apennine or Mediterranean (34.1), the East Apennine or Adriatic (31), and the Sicilian (20.1). Other meteorologists dwell on the difference in rainfall on the two sides of the Po, assigning 36 inches to the Transpadane, and 26 to the Cispadane regions.