It’s sensible to visit Ivory Coast between November and March, when the heat and humidity are a little lower and rainstorms are rarer. At this time of year there are fewer malaria-carrying mosquitoes and most of the national parks are open to the public before shutting for the wet season (June to October).
If you’re planning to explore the west, avoid going between June and October when showers can cause rapid deterioration of roads and hiking paths. Those tempted by the north ought to get there before the harmattan season begins in June, as the dust can ruin visibility for sightseeing and photography, and irritate uncovered eyes, mouths and noses.
Due to its location some 400km from the equator, Ivory Coast is generally hot and humid, day and night, all through the year. However, there are minor regional variations. While the national daytime temperatures average 26.6°C, the equatorial south of the country regularly exceeds 30°C. The tropical centre is a little cooler and the arid and semi-arid north is colder at night due to lower humidity. In the periods of June to September and December to January, temperatures in the high-altitude Dix-Huit Mountains in the west can fall as low as 15°C. The average relative humidity is 71% in the north and 85% in the south.
Ivory Coast has three seasons, the third of which is more discernible than the first two. From November to March, the climate is typically warm and dry with occasional rainfall. March to May is hotter and drier, with very little rain. June to October is the hot, rainy season, during which the west and southwest are stricken with heavy downpours. Towns like Touba, on the Liberian border, experience up to 2,300mm of rainfall per annum. During the same period, there are lighter rains in the south, north and – to a lesser degree – the centre and east. An average of 1,847mm of rain a year falls on Abidjan, on the south coast, whilst the far northern outpost of Odienné sees 1,500mm, and Bouaké in the centre and Bondoukou in the east both receive just 1,100mm. The national average annual precipitation is 1,289mm.
In the first six months of the year, the warm maritime air mass thrusts north over Ivory Coast in a reaction to the movement of the sun. At the front of the mass, an inter-tropical front brings rain, hot air and prevailing winds from the southwest. Around December, this cycle reverses and the continental air mass travels south over the country, causing the harmattan, a dry and dusty trade wind, to sweep down from the Sahara Desert and over the northern and central parts of Ivory Coast. While the harmattan rarely travels faster than 20km/h, it can be strong enough to stir up small dust storms, decreasing visibility to as little as 1km. On the odd occasion over the years, the harmattan has been so powerful that it has felled trees, flattened crops and knocked over flimsy buildings.