December weather in Sri Lanka, region by region

In December the northeast monsoon is fully established. The wind blows from the Bay of Bengal across the island, dropping its rain on the east coast, the north and the eastern slopes of the hills, then descending as a drier wind over the west and south. That makes December the start of the southwest's long dry season and the peak of the east's wet season.

Early December can still feel like November, with afternoon storms on the southwest coast. By the second half, especially around Christmas, the south and west are usually dry, sunny and calm. Cyclone risk persists into December, mainly for the east and north.

Temperatures dip slightly. Coastal highs are around 29 to 30 °C, and nights in Nuwara Eliya fall to about 10 °C.

Colombo averages roughly 150 to 180 mm of rain in December, much of it in the first ten days. Galle, Mirissa, Bentota and Tangalle follow the same pattern. By the second half of the month, long dry spells and calm seas are the norm, and the swimming beaches on the south coast are at their best.

Whale-watching from Mirissa runs regularly, the surf breaks at Weligama, Midigama and Hikkaduwa are in season, and the sea is clear for snorkelling at Unawatuna and Hikkaduwa. Humidity drops, and evenings are pleasant.

Demand is the main challenge. Christmas and New Year are the busiest weeks of the year on the south coast, and hotels and transport book out early.

The hills clear through December. Rain falls mainly on the eastern side, around Ella and Badulla, from the northeast monsoon, while Nuwara Eliya and the western slopes become drier. Nuwara Eliya averages roughly 150 to 200 mm in December, falling into January.

The Adam's Peak pilgrimage season usually opens at the Unduvap full moon in December, and from then the path is lit at night. Clear pre-dawn skies become more frequent through the month. Nights in Nuwara Eliya fall to about 10 °C, and the first ground frosts can appear late in December.

The Cultural Triangle receives northeast monsoon rain in December, with Sigiriya and Polonnaruwa averaging roughly 200 to 250 mm, more in the east of the region. Early December can bring long wet spells; the second half is usually drier, with showers rather than storms.

The landscape is at its greenest and the tanks are full. Highs are about 29 to 30 °C, the most comfortable of the year for climbing. Morning mist sometimes sits on the plains around Sigiriya.

December is the wettest month in much of the east and north. Trincomalee averages roughly 350 to 400 mm, Batticaloa similar or more, and Jaffna roughly 250 to 350 mm. Rain often falls for long periods, and the northeast wind brings rough seas onto every east coast beach.

Flooding is possible on low-lying roads in the east when a depression passes. Many east coast beach hotels are closed or quiet. Arugam Bay is out of season.

The December route follows the dry side: the Cultural Triangle, the hills and the south or west coast, with the beach at the end. If the trip starts early in December, put the beach in the second half of the month.

December is peak season, so book early, especially for Christmas and New Year. Lankan Stays & Trails plans December trips on the dry side of the island and leaves the east coast for the summer months.