What to Pack for Sri Lanka: The Tested, No-Nonsense Packing List

I've packed for Sri Lanka five times, and each time I've refined my list based on what I actually used versus what sat untouched at the bottom of my bag. This is the final, definitive version — tested across monsoon and dry seasons, beach and mountains, jungle and city.
The Essential Rule
Sri Lanka's climate varies dramatically by region and altitude. You can be sweating on a 35°C beach in the morning and shivering at 5°C on a mountain summit by evening. Pack layers, not bulk.
The Core Kit
Three moisture-wicking t-shirts, two pairs of lightweight hiking trousers that convert to shorts, one pair of proper hiking boots (not trainers), one pair of sandals for beach/town, a packable rain jacket, a warm fleece for the highlands, and a wide-brimmed sun hat.
