Overall climate is cool and dry. The east coast is warmer than the west, especially in summer, as a branch of the southern equatorial current reaches its shores, whereas the west coast is washed by a cold current. However, winters are colder on the inland plateaus east of the slopes and further down the coast on the south east end of the Patagonian region. For example at Puerto Montt, on the inlet behind Chilo� Island, the mean annual temperature is 11 �C (52 �F) and the average extremes 25.5 �C (77.9 �F) and ?1.5 �C (29.3 �F), whereas at Bah�a Blanca near the Atlantic coast and just outside the northern confines of Patagonia the annual temperature is 15 �C(59 �F) and the range much greater, as temperatures above 35 �C and below ?5 �C are recorded every year. At Punta Arenas, in the extreme south, the mean temperature is 6 �C (43 �F) and the average extremes 24.5 �C (76.1 �F) and ?2 �C (28 �F). The prevailing winds are westerly, and the westward slope has a much heavier precipitation than the eastern in a rainshadow effect; the western islands close to Torres del Paine receive an annual precipitation of 4,000 to 7,000 mm, whilst the eastern hills are less than 800 mm and the plains may be as low as 200 mm annual precipitation.
Precipitation is highly seasonal in northwestern Patagonia (for example, Villa La Angostura, in Argentina and right next to Chile, receives up to 434 mm of rain and snow in May, 297 mm in June, 273 in July, compared to 80 in February and 72 in March. The total for the city is 2074 mm, making it one of the rainiest in Argentina. Further west, some areas receive up to 4,000 mm and more, especially on the Chilean side. In the northeast, the seasons for rain are reversed: most rain falls from occasional summer thunderstorms, but totals barely reach 500 m in the northeast corner, and rapidly decrease to less than 300 mm. The Patagonian west coast, which belongs exclusively to Chile, has a cool oceanic climate, with summer temperatures
