The best time to visit Jaffna is from December to March, when the northeast monsoon has passed and the weather is dry and relatively cool. April and May bring rising heat before the southwest monsoon season begins. The north of Sri Lanka has a different monsoon pattern from the south: its wet season runs roughly October to January, while the south is wet from May to September. This makes Jaffna a good option during the southern Sri Lanka rainy season.
The Nallur Festival, held over 25 days in July and August, is worth planning a visit around if you can handle the heat. The processions, chariot ceremonies, and sheer scale of the devotion are extraordinary. Accommodation in Jaffna books out during the festival and prices rise — plan ahead.
Water access to the islands can be disrupted by weather at any time; the winter months offer the most reliable sea conditions for the ferry crossings to Nainativu and Delft.