As a large island, Madagascar enjoys a diversity of climates, depending on the regions you travel through. Broadly speaking, there are three main zones:
East coast: A humid tropical climate with frequent rainfall, especially between December and March.
Highlands: A more temperate climate, cool and dry during the austral winter (May to October), with cool nights.
West and South Coast: A semi-arid climate, warmer and sunnier, with little rain, even during the wet season.
During the dry season (April to October), days are generally sunny, with temperatures ranging from 20 to 25°C in the highlands and up to 30°C on the coasts. Nights can be cool, especially at higher altitudes (10 to 15°C in Antananarivo). So opt for light, breathable clothing during the day, but don't forget warm layers for the evenings and rain gear.
Don't hesitate to consult general information websites or the list in your detailed travel program to find out what clothes to pack.