🇬🇼Guinea-Bissau

Guinea-Bissau spans 10°56′–12°41′N, a small West African country of approximately 36,125 km² on the Atlantic coast between Senegal and Guinea. The terrain comprises a low mainland with the highest point reaching only around 262 m in the southeastern Boé hills, heavily indented by mangrove estuaries along the Geba, Mansoa, and Cacheu rivers, plus the offshore Bijagós Archipelago of roughly 88 islands.

The climate is uniformly tropical savanna Aw with a tropical monsoon Am tendency on the wetter southern coast, modulated by the West African monsoon, the dry Harmattan winds from the Sahara, and the cool Atlantic Canary current flowing along the coast.

Bissau on the coast averages 24°C in January and 27°C in August with 1,950 mm of rainfall almost entirely concentrated between June and October, followed by a long bone-dry Harmattan-influenced winter from November to May. Bafatá in the interior records 28°C annually with 1,560 mm, while the Bijagós Archipelago receives 1,800–2,200 mm and maintains high humidity year-round.

Relative humidity ranges from 50% in the dry Harmattan months to 90% during the wet season, and sea-surface temperatures range from 21°C in February to 27°C in October. Major climate hazards include severe Sahel-belt droughts—notably 1972–73 and 1982–84—that crippled rice and cashew production, intensifying coastal erosion threatening Bissau harbour and the Bijagós islands, recurrent severe wet-season urban floods in Bissau during 2020 and 2022, accelerating mangrove loss along the Geba and Cacheu estuaries, and sea-level rise putting the densely populated coastal mangrove zone comprising around 25% of the country under growing salinisation pressure.

Our archive covers 1 Bissau-Guinean cities with daily ERA5 reanalysis data going back to 1940. The warmest July averages occur in Bissau, around 28.9°C, while Bissau records the coldest January nights near 20.5°C. Comparing the last decade against the 1940–1970 baseline, mean temperatures across these cities have risen by about 1.2°C.