Tropical climates (Köppen Group A) are characterised by year-round warmth (monthly mean >18°C), high humidity, and no true winter. Three subtypes: rainforest (Af: Singapore, Kuala Lumpur), monsoon (Am: Mumbai, Bangkok), and savanna (Aw: Nairobi, Bangkok dry season). Fabric priorities: maximum breathability (linen 0.95, hemp 0.90), high moisture regain (merino 15%, viscose 13%), loose weaves (voile, seersucker). Avoid: heavy wool, denim, velvet, canvas.