Maputo sits just inside the tropics and has two seasons: a hot, humid wet summer from November to March, and a warm, dry winter from May to September. April–September is the most comfortable time to visit — daytime temperatures of 24–28°C, low humidity, almost no rain, and the bay calm enough for the ferry to Inhaca to run reliably. Avoid January and February if you can: this is cyclone season for southern Mozambique, and rainfall can paralyse the city's drainage for days.
The big cultural events worth timing a trip around are the AZGO music festival in late May, which brings African and international acts to Maputo over a long weekend, and the DOCKANEMA documentary film festival in September. The independence holiday on 25 June is a good day to be in town — the city dresses up and bars stay open late.