Climate

Abstract

Being located in the low latitudes between 6° and 10° N and surrounded by the warm Indian Ocean, Sri Lanka shows a very typical tropical monsoonal climate, meaning it is hot and humid all year round with distinct wet and dry seasons. Rainfall of Sri Lanka is of multiple origins. Monsoonal, convectional, and synoptic-scale “weather systems” formed in the Bay of Bengal account for a major share of the annual rainfall. It varies from 900 mm (southeastern lowlands) to over 5,500 mm (southwestern slopes of the Central Highlands). Sri Lanka is also at risk of cyclones and intense tropical storms, which have been known to lash the island during the months of October to December. On the basis of average annual rainfall along with some other biophysical parameters, Sri Lanka has been generalized into three major climatic zones in terms of “Wet Zone” in the southwestern region including Central Highlands country, “Dry Zone” covering predominantly, northern and eastern part of the country, and being separated by an “Intermediate zone,” skirting the Central Highlands except in the south and the west. The spatial differences in temperature in Sri Lanka are due to altitude; there is no temperature variation due to latitude. The mean monthly temperatures differ slightly depending on the seasonal movement of the sun, with some modifying influence caused by rainfall. In the lowlands, the mean annual temperature is 27 °C and the mean daily range is 6 °C. In the Central Highlands with altitudes up to 2,400 m a cooler climate is experienced.