The north-east monsoon is properly established in December. The south coast does what it does from now until March: clean mornings, dependable waves, and a string of breaks between Hikkaduwa and Mirissa that suits everybody from a first lesson in Weligama bay to the reefs at Midigama. The east coast has been shut since October.
The forecast is not what you plan around. The island fills from about the twentieth and stays full into the second week of January, and Weligama in particular is small. The first fortnight is the same surf with half the boards on it, and it is the single most useful thing anybody can tell you about a December trip here. The second fortnight is the busiest stretch of the Sri Lankan year.
That makes the choice of village heavier in December than in any other month, because what varies between them is the crowd and not the wave. Weligama is the shortest transfer and the only sand, so it fills first and hardest. Midigama has four reefs over two kilometres and room on them even now, and is dark by nine. Ahangama has The Rock, which holds the best measured week on the island, and it has the evenings: rooftops, kitchens worth the walk, cafés that open early, and enough people arriving alone that nobody eats alone. In the busiest fortnight of the year that is either exactly why you are there or exactly why you are not.
Five coasts in the world are at their own peak in December and Sri Lanka is the warmest of them by eight degrees: 28°C against 20 in the Canaries and 18 in Morocco, with Spain at 14. If you are weighing a Christmas trip against a European one, that is the number the decision turns on, and the second number is that the Canaries and Morocco both rate a level below Sri Lanka for anybody still learning.

