Key Summary- Guinea-Bissau has a tropical monsoon climate (Am) along the coast and islands and a tropical savanna climate (Aw) inland, both driven by the West African monsoon.
- A six-month rainy season (June–October) brings heavy downpours and high humidity, while the dry season (November–May) moves from hazy harmattan winds to hotter, sunnier weather.
- Flat coastal plains, mangroves, and the Bijagós Archipelago keep temperatures warm year-round, but rainfall contrasts sharply between the lush coast and the drier interior.
Guinea-Bissau sits in the tropics (10°N–13°N) and its low-lying, deeply indented Atlantic coastline exposes it fully to the West African monsoon. Our Köppen climate map at WeatherBox shows two dominant zones. The tropical monsoon climate (Am) cloaks the coastal belt and the Bijagós Archipelago, where over 2,000 mm (80 in) of rain falls mainly during the long summer monsoon. Inland, the tropical savanna climate (Aw) takes over, with a shorter intense wet season and a longer, much drier period. Daytime highs typically hover between 30°C and 34°C (86°F–93°F) and nights rarely drop below 20°C (68°F) any month. With no mountains to break the trade winds or generate relief rainfall, the entire country is a flat alluvial plain threaded by rivers and mangroves, so temperature shifts are seasonal rather than altitudinal.
The monsoon’s arrival in June soaks the landscape in dazzling green. In Am-zone coast and islands, frequent afternoon downpours and stubbornly high humidity swell the mangrove channels, creating excellent conditions for spotting hippos, manatees, and migratory birds in the Bijagós labyrinth. The interior Aw zone around Bafatá and Gabú greens dramatically during its rains, but by November the savannah browns. The dry season opens with the harmattan, a dusty Sahara wind that from December to February casts atmospheric haze over Bissau Velho’s colonial architecture. By March the dust clears, and the heat builds markedly until the next rains arrive in June. The Bijagós Islands often catch occasional off-season showers, staying greener longer.
For most visitors, the optimal time is December to February, when blue skies dominate and the harmattan haze takes the edge off the tropical heat. November and early March can be decent shoulder months, though some rural roads remain muddy in November, and March brings notably high temperatures. The rainy season, especially July to September, turns unpaved roads into quagmires, amplifies mosquito activity, and pairs extreme humidity with heavy downpours that can complicate travel. Nonetheless, this is when the country’s mangroves and forests are at their most intense green, and visitor numbers are low. Pack lightweight, breathable clothing year-round, along with a wide-brimmed hat and strong sunscreen. In the monsoon, add a sturdy raincoat, waterproof footwear, and insect repellent; during harmattan months, a cotton scarf helps filter dusty breezes. Guinea-Bissau’s climate is a straightforward wet-dry story, and your experience depends on which chapter you choose. Explore WeatherBox’s detailed monthly charts to compare rainfall and temperatures across Bissau, the Bijagós, and inland stations before you finalise your itinerary.
