The south-west monsoon is having its final say, with high rainfall expected along the western and southern coasts (avg temp: 28°C). Rainfall also increases in the Tea Country, although further north, in the Cultural Triangle, drier weather is expected, with plenty of sunshine.
Across the country cyclones can occur, especially towards the end of September and into October and November, bringing with them heavy rain and high winds. The east coast is expecting its final month of good weather, meaning that towards the end of the month rainfall is expected to increase.
September is a mixed bag in terms of weather. Sri Lanka's interior remains hot and humid, with a high chance of rainfall, although downpours are typically short and intense. During this period of dry, arid weather conditions Yala National Park often closes for the whole month to allow animals to roam freely in search of water.
Despite high average temperatures, swimming in the sea on Sri Lanka's south and west coasts is often not recommended this month due to rough seas and many hotels will have their red flags out to indicate that swimming is dangerous.
Sri Lanka's east coast is expecting its final month of good weather, so if it's beach time you're looking for then head to Passekudah and Trincomalee. Although towards the end of September rainfall is expected to increase along the east.
The south-west (the section south of Negombo & Colombo) and the entire south coast: Monsoon season but less rain than in previous months
The entire east coast: Peak season.
The central and northern section of the west coast (from Negombo northwards): Peak season (sunshine expected but with high winds and sea’s).