In general, it is best to travel in Africa during the dry season as it’s cooler and there are fewer bugs about. For Madagascar, this means travelling between about May and October. If you want to see the humpback whale migration, plan to travel between June and September.
January to March is cyclone season and it’s best not to travel then. The lemur breeding season is from October to December when babies are born to take advantage of the new spring foliage, although December is generally Madagascar’s wettest month.