Climate varies with elevation and region. Generally, however, Italy is included between the annual isotherms of 11° C and 19° C (52° F and 66° F ). The coldest period occurs in December and January, the hottest in July and August. In the Po Plain, the average annual temperature is about 13° C (55° F ); in Sicily, about 18° C (64° F ); and in the coastal lowlands, about 14° C (57° F ). The climate of the Po Valley and the Alps is characterized by cold winters, warm summers, and considerable rain, falling mostly in spring and autumn, with snow accumulating heavily in the mountains. The climate of the peninsula and of the islands is Mediterranean, with cool, rainy winters and hot, dry summers. Mean annual rainfall varies from about 50 cm (20 in) per year, on the southeast coast and in Sicily and Sardinia, to over 200 cm (80 in), in the Alps and on some westerly slopes of the Apennines. Frosts are rare in the sheltered western coastal areas, but severe winters are common in the Apennine and Alpine uplands.