Sri Lanka occupies 65,610 square kilometers in the Indian Ocean, positioned between 5°55' and 9°51' north latitude and 79°41' and 81°53' east longitude. The island sits approximately 31 kilometers off the southeastern coast of India, separated by the Palk Strait to the northwest and the Gulf of Mannar to the west. Adam's Bridge, a chain of limestone shoals stretching 48 kilometers between Mannar Island and Rameswaram in India, surfaces intermittently above sea level and represents the closest physical connection between the two landmasses. The island's maximum length measures 432 kilometers from Point Pedro in the north to Dondra Head in the south, while the maximum width spans 224 kilometers.
The topography divides into three distinct elevation zones. Coastal plains extend inland between 8 and 80 kilometers, maintaining elevations below 100 meters and encircling the entire island. The Central Highlands dominate the south-central interior, comprising approximately 20 percent of the total land area with elevations exceeding 1,500 meters. Pidurutalagala rises to 2,524 meters near Nuwara Eliya, making it the highest point in Sri Lanka. The Knuckles Mountain Range extends northeast from Kandy, reaching elevations of 1,863 meters at Knuckles Peak and covering 155 square kilometers designated as a conservation forest in 2000. Between the coastal plains and central massif, an intermediate peneplain zone transitions through rolling hills and river valleys.
The climate divides Sri Lanka into two primary zones determined by monsoon patterns and topographic barriers. The Wet Zone occupies the southwestern quarter of the island and the entire Central Highlands, receiving between 2,500 and 5,000 millimeters of annual rainfall. The southwest monsoon delivers precipitation from May through September, while the northeast monsoon contributes additional rainfall from December through February. Colombo records an average annual rainfall of 2,400 millimeters distributed across approximately 147 rainy days. The Dry Zone encompasses the northern and eastern lowlands, receiving between 1,200 and 1,900 millimeters annually, with Trincomalee averaging 1,650 millimeters concentrated primarily during the northeast monsoon period from October through January. A transitional zone between these regions experiences intermediate rainfall patterns.
Temperature variation correlates directly with elevation rather than seasonal change. Coastal areas maintain mean temperatures between 26°C and 28°C throughout the year, with diurnal variation rarely exceeding 5°C. Colombo records average maximum temperatures of 31°C and minimum temperatures of 23°C. The Central Highlands experience significantly cooler conditions, with Nuwara Eliya at 1,868 meters elevation maintaining average maximum temperatures of 18°C and minimum temperatures of 11°C. Temperatures can drop to 5°C during December and January in the highest elevations. Humidity remains consistently high across all zones, ranging from 70 percent during daytime hours to 90 percent overnight in coastal regions.
The Mahaweli River extends 335 kilometers from the Central Highlands near Adam's Peak to the Indian Ocean at Trincomalee, making it the longest waterway in Sri Lanka. The Mahaweli Ganga development project, initiated in 1970 and substantially completed by 1985, constructed four major reservoirs and several diversion tunnels to generate hydroelectric power and provide irrigation to 128,000 hectares in the Dry Zone. The river's catchment area covers 10,327 square kilometers, approximately 16 percent of the island's total land area. Other significant rivers include the Kelani River, which flows 145 kilometers westward from the Central Highlands to Colombo, and the Kalu River, extending 129 kilometers through the southwestern Wet Zone.
Sinharaja Forest Reserve encompasses 111.9 square kilometers of tropical lowland rainforest in southwestern Sri Lanka, with elevations ranging from 300 to 1,170 meters. UNESCO designated Sinharaja a World Heritage Site in 1988, recognizing its status as the last viable area of primary tropical rainforest in Sri Lanka. The reserve receives between 3,500 and 5,000 millimeters of annual rainfall, with no true dry season. Scientific surveys document 830 endemic plant species, 217 woody plant species, and 139 endemic tree species within the reserve boundaries. The canopy height averages 35 to 40 meters, with emergent dipterocarp trees reaching 45 to 50 meters.
Horton Plains National Park covers 31.6 square kilometers of montane grassland and cloud forest between 2,100 and 2,300 meters elevation. The plateau receives approximately 2,500 millimeters of annual rainfall, primarily during the southwest monsoon from May through August and the northeast monsoon from October through January. World's End, a precipice at the southern edge of the plateau, drops 870 meters vertically to the valley below, with Baker's Falls descending 20 meters along Belihul Oya stream. Temperature variations range from 0°C to 27°C, with frost recorded during January and February. The park supports 750 plant species, including 55 endemic species, and serves as the watershed for three major river systems: Mahaweli, Kelani, and Walawe.
Yala National Park extends across 979 square kilometers in the southeastern coastal region, making it the second largest national park in Sri Lanka after Wilpattu. The park divides into five blocks, with Block I covering 141 square kilometers and receiving the majority of visitor access. Yala combines six distinct habitat types: coastal lagoons, rocky outcrops, open parkland, scrub jungle, brackish water areas, and riverine forest. Annual rainfall averages 1,000 millimeters, concentrated between October and January during the northeast monsoon. Scientific estimates place the leopard density in Block I between 10 and 15 individuals per 100 square kilometers, among the highest concentrations documented globally for this species.
Wilpattu National Park encompasses 1,317 square kilometers northwest of Anuradhapura, representing the largest national park in Sri Lanka. The park reopened to visitors in 2010 after closure during the civil conflict period. Wilpattu contains approximately 60 natural lakes called willus, formed in depressions on the sand bed and filled by rainwater. These seasonal wetlands range from 1 to 50 hectares in size. The park receives between 1,000 and 1,200 millimeters of annual rainfall, creating conditions suitable for dry zone vegetation including extensive stands of Manilkara hexandra forest. Survey data from 2015 documented 31 mammal species within park boundaries.
The central highlands produce distinct microclimates that support specialized ecosystems. Knuckles Conservation Forest contains 34 forest types identified through botanical surveys, including tropical lowland rainforest below 900 meters, submontane forest between 900 and 1,500 meters, and montane forest above 1,500 meters. The range receives between 2,500 and 5,000 millimeters of annual rainfall depending on aspect and elevation. Peak Wilderness Sanctuary encompasses 224 square kilometers surrounding Adam's Peak, protecting montane and submontane forest types. The sanctuary receives approximately 3,500 millimeters of annual rainfall, with heavy precipitation during both monsoon periods creating year-round cloud forest conditions on upper slopes.
Sri Lanka's coastline extends 1,340 kilometers, combining sandy beaches, rocky headlands, coastal lagoons, and mangrove systems. Coral reef formations occur along the southwestern, southern, and northeastern coasts, with fringing reefs extending between 50 and 200 meters offshore. Hikkaduwa Marine National Park protects 10.1 square kilometers including 4.9 square kilometers of coral reef established in 1979. Pigeon Island National Park off Trincomalee covers 471.4 hectares, with two small islands surrounded by coral reefs supporting 100 species of coral and 300 species of reef fish according to survey data collected between 2000 and 2005. The continental shelf extends between 20 and 30 kilometers offshore along most of the island, with the 200-meter depth contour located 10 to 15 kilometers from the coast in the south and west.