South Georgia and The South Sandwich Islands - Climate

Climate

The climate is classified as polar, and the weather is highly variable and harsh. Typical daily maximum temperatures in South Georgia at sea level are around 0 °C (32 °F) in winter (August) and 8 °C (46.4 °F) in summer (January). Winter minimum temperatures are typically about −5 °C (23 °F) and rarely dip below −10 °C (14 °F). Annual precipitation in South Georgia is about 1,500 mm (59.1 in), much of which falls as sleet or snow, which is possible in any month. Inland, the snow line in summer is at an altitude of about 300 m (984 ft).

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 8 knots 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 just 21.5% of possible. This amounts to around 1000 hours of sunshine annually. However, the local topography also contributes significantly to the low insolation. A study around 1960 showed sunshine recording instruments were obscured entirely during June, and significantly in other months. It was estimated theoretical sunshine exposure minus obstructions would be around 14% at Bird Island, and 35% at King Edward point—or in hourly terms ranging from around 650 hours in the West to 1500 hours in the East, illustrating the effect the Allardyce range has in breaking up cloud cover.

During mountain wind conditions, the winds blow straight up the western side and straight down the eastern side of the mountains and become much warmer and drier; this produces the most pleasant conditions when temperatures can occasionally rise over 20 °C (68 °F) on summer days. The highest recorded temperature was 28.8 °C (83.8 °F) at Grytviken. and 26.3 °C (79.3 °F) at nearby King Edward point, both on the sheltered East side of the Islands. Conversely, the highest recorded temperature at Bird Island on the windward Western side is a mere 14.5 °C (58.1 °F). As one might expect, the sheltered eastern side can also record lower winter temperatures—the absolute minimum for Grytviken being −19.4 °C (−2.9 °F), King Edward Point −18.9 °C (−2.0 °F), but Bird Island just −11.4 °C (11.5 °F)

The seas surrounding South Georgia are cold throughout the year due to the proximity of the Antarctic 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 to 0 °C (32 °F) in late August and rise to around 4 °C (39.2 °F) only in early April.

The South Sandwich Islands are much colder than South Georgia, being further south and more exposed to cold outbreaks from the Antarctic continent. They are also surrounded by sea ice from the middle of May to late November (even longer at their southern end). Recorded temperature extremes at South Thule Island have ranged from −29.8 °C (−21.6 °F) to 17.7 °C (63.9 °F).