Benin's climate is hot and humid. Annual rainfall in the coastal area averages 36 centimeters (14 inches), not particularly high for coastal West Africa. Benin has two rainy and two dry seasons. The principal rainy season is from April to late July, with a shorter less intense rainy period from late September to November. The main dry season is from December to April with a short cooler dry season from late July to early September.
Temperatures and humidity are high along the tropical coast. In Cotonou, the average maximum temperature is 31°C (89°F); the minimum is 24°C (75°F). Variations in temperature increase when moving north through a savanna and plateau toward the Sahel. A dry wind from the Sahara called the harmattan blows from December to March. Grass dries up, the vegetation turns reddish brown, and a veil of fine dust hangs over the country, causing the skies to be overcast.