Porto-Novo sits on the coast of southern Benin in a zone with two wet seasons — a longer one from April to July and a shorter one from October to November. The driest and most comfortable months for visiting are December through February, when the harmattan wind blows in from the Sahara and temperatures are cooler. March and April are hot and humid before the rains arrive.
The Grand Marché d'Adjara rotates on a four-day cycle year-round; checking when the next market day falls is worth doing before you arrive. Benin celebrates a national Voodoo Day on 10 January, and the ceremonies and festivals around this date — concentrated in Ouidah but felt across the south — are worth timing a visit around if you have a particular interest in Vodun culture.