The 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 Chiloé Island, the mean annual temperature is 11 °C (52 °F) and the average extremes are 25.5 and −1.5 °C (77.9 and 29.3 °F), whereas at Bahía 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 are 24.5 and −2 °C (76.1 and 28.4 °F). The prevailing winds are westerly, and the westward slope has a much heavier precipitation than the eastern in a rainshadow effect;[14] 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.