The best time to visit Sri Lanka is generally from December to March, marking the dry season in most tourist parts of the country. However, Sri Lanka is a year-round destination, with April/May to September being the ideal time to explore the East Coast of Sri Lanka.
Sri Lanka experiences two different monsoon seasons at different times. So, it implies that where one part of the country is wet, the other can be dry simultaneously.
Peak Season: December to March is the best time to visit Sri Lanka on the western and southern coasts. These months are optimal for exploring beach destinations like Mirissa, Galle, or Colombo, and even the highland destinations of Ella and Nuwara Eliya. The temperature ranges from 25°C to 30°C on the coasts and 15°C to 18°C in the highlands, offering pleasant weather for outdoor activities.
Shoulder Season: April, September, and October constitute the shoulder season with fewer crowds, but it's not rainy during these months.
Off-Season: May to August is the off-season. Frequent showers and higher humidity can characterize the weather in the touristy southern coast. Travelers during these months may experience limitations in outdoor activities and sightseeing due to the rain. However, this is a very good season to explore the East Coast of Sri Lanka, such as Trincomalee, Arugam Bay, etc. with dry weather and clear skies.