about and rarely dip below . Annual precipitation in South Georgia is about , much of which falls as sleet or snow, which is possible the entire year. Inland, the snow line in summer is at an altitude of about . Westerly winds blow throughout the year interspersed with periods of calm—indeed, in 1963, 25% of winds were in the calm category at King Edward Point, and the mean wind speed of around is around half that of the Falkland Islands. This gives the eastern side of South Georgia (leeward side) a more pleasant climate than the exposed western side. The prevailing weather conditions generally make the islands difficult to approach by ship, though the north coast of South Georgia has several large bays which provide good anchorage. Sunshine, as with many South Atlantic Islands, is low, at a maximum of just 21.5%. This amounts to around 1,000 hours of sunshine annually. The local topography, however, also contributes significantly to the low insolation. A study published during the early 1960s indicated that sunshine recording instruments remained significantly obscured throughout the year and entirely obscured during June. It was estimated that the theoretical sunshine exposure minus obstructions would be around 14% at Bird Island and 35% at King Edward Pointor, in hourly terms, ranging from around 650 hours in the west to 1,500 hours in the east. This illustrates the effect the Allardyce Range has in breaking up cloud cover. Mountain winds rise over the western slopes of the mountains of South Georgia and down the eastern side and become much warmer and drier due to the Föhn effect; this produces the most pleasant conditions when temperatures can occasionally rise to over on summer days. The highest temperature recorded at the King Edward Point meteorological station (often generically and less accurately called Grytviken) on the sheltered eastern side of South Georgia is . Conversely, the highest recorded temperature at Bird Island on the windward western side is a mere . As one might expect, the sheltered eastern side can also record lower winter temperatures—the absolute minimum temperature for King Edward Point is , but Bird Island just . The seas surrounding South Georgia are cold throughout the year due to the proximity of the Antarctic Circumpolar Current. They usually remain free of pack ice in winter, though thin ice may form in sheltered bays, and icebergs are common. Sea temperatures drop