Sri Lanka is a fantastic destination all year round. I'd recommend visiting the South West Coast region between October-April and the East Coast from May - September. Sri Lanka offers amazing culture, history, nature, wildlife, cuisine and beaches!
Stay at the Geoffrey Bawa properties spread throughout Sri Lanka to get a unique experience which combines the islands architectural heritage with natural landscapes-Heritance Kandalama, Kandy House, Lighthouse Hotel, The Vila Bentota just to name a few. The 98 Acres Resort in Nuwara Eliya is another hidden gem surrounded by a tea estate up in the hillside.
There are so many things to see and do while in Sri Lanka, a few top picks include: Sigiriya Rock Fortress, Anuradhapura Ancient Capital, Sacred Tooth Relic a Buddhist temple in Kandy, tea plucking and blending in Nuwara Eliya, Yala National Park and a river safari in Bentota or just hire a villa in Galle if you just want to relax by the beach.
You can't go past delicious, local Sri Lankan cuisine! Ministry of Crab at the Dutch Hospital shopping precinct in Colombo is well-known for seafood - make sure you try a fish curry Kottu, isso vadai and hoppers are popular street eats and traditional samosas, fish rolls and vegetable roti will have your taste buds tingling.