Cotonou, the largest city of Benin, sits on the Gulf of Guinea coast of West Africa, on a narrow strip between the Atlantic Ocean and Lake Nokoué at approximately 6.37°N, 2.42°E. It has a tropical wet-and-dry climate (Köppen Aw) — hot and humid year-round — with an unusual pattern of two rainy seasons and two dry seasons, and its coastal position keeps temperatures fairly steady while the sea breeze tempers the heat.

There is no summer in the temperate sense: temperatures stay warm all year, with daytime highs around 28–31°C and warm, humid nights. The main rainy season runs from around April to July, when the heaviest rain falls and cloud and humidity keep the heat in check; the hottest, most humid conditions tend to come in the drier spells between the rains, when the sun beats down on the muggy coast.

There is no true winter, but the main dry season from around November to March is the most settled time, warm and sunnier with somewhat lower rainfall. Its most distinctive feature is the Harmattan, a dry, dusty wind that can blow off the Sahara mainly between December and February, hazing the sky and briefly lowering the humidity, though it reaches the coast less strongly than the interior.

Cotonou receives on the order of 1,200–1,300 mm of rain a year, delivered in two pulses typical of the Guinea coast: a main rainy season from April to July, with a peak around June, and a shorter secondary wet spell around September and October, separated by a drier interval in August. Live rainfall, humidity, and pressure readings for the city are shown in the panels above.

Cotonou's double rainy season — a strong one in early summer and a weaker one in autumn, split by a short dry break — is characteristic of the West African Guinea coast and sets the rhythm of its year. The Harmattan of midwinter, carrying Saharan dust toward the coast, is its other distinctive feature, while the ever-present humidity and the sea breeze off the Gulf of Guinea shape daily life in the low-lying, lagoon-fringed city.

To follow any single measurement in Cotonou more closely, use our live instruments: the online barometer for atmospheric pressure, the thermometer for temperature, the hygrometer for humidity, the anemometer for wind speed, the wind vane for wind direction, and the rain gauge for rainfall.