You arrive in Zanzibar after lunch, the air feels hot and damp, and a dark cloud is building over Stone Town. Two hours later, the street is dry again. That is late May: still warm, often quiet, and too changeable for a rigid beach-only holiday. The good news is that this timing can work very well. You get fewer crowds, green spice plantations, cooler evenings than the hottest months, and a better chance of finding calm corners on the coast. The bad news is simple: May sits at the end of the main rainy season, so anyone expecting guaranteed blue…