The island covers an area of 25 square kilometres (2,500 ha). The eastern side is wetter than the western. Although the climate is essentially arid, the rainfall does average 1000 mm annually, but with considerable variation over the terrain. Summer is from May to November, which is also the rainy season. Winter from December to April is the dry season. Sunshine is very prominent for nearly the entire year and even during the rainy season. Humidity, however, is not very high due to the winds. The average temperature is around 25 °C with day temperatures rising to 32 °C. The average high and low temperatures in January are 28 °C and 22 °C, respectively, while in July they are 30 °C and 24 °C. The lowest night temperature recorded is 13 °C. The Caribbean sea waters in the vicinity generally maintain a temperature of about 27 °C.