Cyclones can occur during rainy season.
Mayotte is a malaria-infested zone. Consult your physician for anti-malaria medecine, and pile on mosquito repellent.
French is the official language and is spoken by roughly 35% of the population. More commonly-spoken are Mahorian a dialect of Swahili and Malagasy.
90% of the population is Muslim, following a very tolerant Islam. Say hello to people you will cross while hiking, always smile, and you will be respected.