The climate of the islands is temperate and oceanic, with a mean air temperature at sea level at Tristan of 15 °C (59 °F), with relatively small daily and seasonal variation. On Gough it is a few degrees colder. Rainfall is high: 1700 mm annually at the Tristan Settlement, and 3300 mm at Gough. Strong winds are common. Mean wind speed is about 40 km/h. Wind speed increases strongly with altitude, while temperature decreases. Thus, while the lowlands experience quite pleasant weather, the uplands may be covered in snow or battered by very strong winds.