the Río de la Plata, the arm of the Atlantic Ocean that separates the south coast of Uruguay from the north coast of Argentina; Buenos Aires lies west on the Argentine side. The Santa Lucía River forms a natural border between Montevideo and San José Department to its west. To the city's north and east is Canelones Department, with the stream of Carrasco forming the eastern natural border. The coastline forming the city's southern border is interspersed with rocky protrusions and sandy beaches. The Bay of Montevideo forms a natural harbor, the nation's largest and one of the largest in the Southern Cone, and the finest natural port in the region, functioning as a crucial component of the Uruguayan economy and foreign trade. Various streams crisscross the town and empty into the Bay of Montevideo. Its coastline near the emptying rivers are heavily polluted. The city has an average elevation of . Its highest elevations are two hills: the Cerro de Montevideo and the Cerro de la Victoria, with the highest point, the peak of Cerro de Montevideo, crowned by a fortress, the Fortaleza del Cerro at a height of . Closest cities by road are Las Piedras to the north and the so-called Ciudad de la Costa (a conglomeration of coastal towns) to the east, both in the range of 20 to from the city center. The approximate distances to the neighboring department capitals by road are, to San Jose de Mayo (San Jose Department) and to Canelones (Canelones Department). Climate Montevideo has a humid subtropical climate (Cfa, according to the Köppen climate classification). Being in a middle latitude, the city experiences the four seasons. It has cool Winters (June to August), warm-hot Summers (December to February), mild Autumns (March to May) and volatile Springs (September to November); The climate is characterized for having mild temperatures, without harsh cold or extreme heat. There are numerous thunderstorms but no tropical cyclones. Rainfall is regular and evenly spread throughout the year, reaching around . Winters are generally cool, wet, windy and overcast. The average temperature during this season is just above . Daytime temperatures are generally between and , and night lows between and . During this season, there are bursts of icy and relatively dry winds of continental polar air masses, giving an unpleasant chilly feeling to the everyday life of the city, with daytime temperatures around or below and