There are two monsoon seasons. South-West monsoon and North-East monsoon.
The south-west monsoon brings rain to the west and southwest coasts and hill country from May to July.
The north-east monsoon hits the east coast from october to January. There is also a inter monsoonal period of unsettled weather preceding in north-east monsoon in october to november during which heavy rainfall and thunderstorms can occur anywhere across the island.
So the best time to visit entire country,
January - April
Mid-July - september
For North and East - February to September
Beach season
January to April - south beaches
May ti July - East beaches
Wildlife
December to April
Bundala National park-birds
South coast - whales
November to April
Kalpitiya - Dolphins
July to September
The cultural Triangle - The gathering of the Elephants
Yala / Wilpattu - leopards http://www.tayafinchonline.com/
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