Sri Lanka is tropical, with distinct dry and wet seasons. The seasons are slightly complicated by having two monsoons.
From May to August the Yala monsoon brings rain to the island’s southwestern half (Colombo, the south, central highland and west coasts) while the dry season here lasts from December to March. The southwest has the highest rainfall – up to 4000mm a year.
The Maha monsoon blows from October to February, bringing rain to the North and East, while the dry season is from May to September.
The North and East are comparatively dry, with around 1000mm of rain annually.
There are also inter-monsoonal periods in April- May and in October – November when rain can occur in many parts of the island.
Colombo and the low-lying coastal regions have an average temperature of 27°C.At Kandy-midland (altitude 500m), the average temperature is 20°C, While Nuwara Eliya – Highland (at 1889m) has a temperate 16°C average. The sea stays at around 27°C all year.
Humidity ranges between 70-90 percent in Colombo, lower in the highlands and cultural triangle. Ocean breezes also moderate temperatures on the coast.
Rainfall is becoming increasingly unpredictable. Sri Lanka averages about 202 cms a year, but figures vary widely from region to region – as the rainfall map shows. The north and east of the island represent the Dry Zone, while the western slopes of the central highlands are wettest.