Across Sri Lanka cyclones can occur, especially towards the end of September and into October and November, bringing with them heavy rain and high winds. Head to the east coast for a chance of the best weather.
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 typically 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.