Sri Lankan Climate
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 5° 55′ to 9° 51′ North latitude and between 79° 42′ to 81° 53′ East longitude, the climate of the island could be characterized as tropical.
The climate is tropical and warm, due to the moderating effects of ocean winds. Mean temperatures range from 17 °C (62.6 °F) in the central highlands, where frost may occur for several days in the winter, to a maximum of 33 °C (91.4 °F) in other low-altitude areas. Average yearly temperatures range from 28 °C (82.4 °F) to nearly 31 °C (87.8 °F). Day and night temperatures may vary by 14 °C (25.2 °F) to 18 °C (32.4 °F).
The rainfall pattern is influenced by monsoon winds from the Indian Ocean and Bay of Bengal. The “wet zone” and some of the windward slopes of the central highlands receive up to 2,500 millimeters (98.4 in) of rain each year, but the leeward slopes in the east and northeast receive little rain. Most of the east, southeast, and northern parts of Sri Lanka comprise the “dry zone”, which receives between 1,200 and 1,900 mm of rain annually.
The arid northwest and southeast coasts receive the least amount of rain at 800 to 1,200 mm per year. Periodic squalls occur and sometimes tropical cyclones bring overcast skies and rains to the southwest, northeast, and eastern parts of the island. Humidity is typically higher in the southwest and mountainous areas and depends on the seasonal patterns of rainfall.
The central part of the southern half of the island is mountainous with heights, more than 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.