Climate in Sri Lanka
Climate is defined as the condition of the atmosphere at a particular location over a long period of time (from one month to many millions of years, but generally 30 years). Climate is the sum of atmospheric elements (and their variations), solar radiation, temperature, humidity, clouds and precipitation (type, frequency, and amount), atmospheric pressure, and wind (speed and direction).
Due to the location of Sri Lanka, within the tropics between 5o 55' to 9o 51' North latitude and between 79o 42' to 81o 53' East longitude, the climate of the island could be characterized as tropical.
The central part of the southern half of the island is mountainous with heights more then 2.5 Km. The core regions of the central highlands contain many complex topographical features such as ridges, peaks, plateaus, basins, valleys and escarpments. The remainder of the island is practically flat except for several small hills that rise abruptly in the lowlands. These topographical features strongly affect the spatial patterns of winds, seasonal rainfall, temperature, relative humidity and other climatic elements, particularly during the monsoon season.
Rainfall in Sri Lanka has multiple origins. Monsoonal, Convectional and expressional rain accounts for a major share of the annual rainfall. The mean annual rainfall varies from under 900mm in the driest parts (southeastern and northwestern) to over 5000mm in the wettest parts (western slopes of the central highlands).
Regional differences observed in air temperature over sri lanka are mainly due to altitude, rather than to latitude. The mean monthly temperatures differs slightly depending on the seasonal movement of the sun, with some modified influence caused by rainfall. The mean annual temperature in Sri Lanka manifests largely homogeneous temperatures in the low lands and rapidly decreasing temperatures in the highlands. In the lowlands, up to and altitude of 100 m to 150 m, the mean annual temperature various between 26.5 0C to 28.5 0C, with an annual temperature of 27.5 0C. In the highlands, the temperature falls quickly as the altitude increases. The mean annual temperature of Nuwaraeliya, at 1800 m sea level, is 15.9 0C. The coldest month with respect to mean monthly temperature is generally January, and the warmest months are April and August.