Nigeria has a tropical climate with variable rainy and dry seasons, depending on location. It is hot and wet most of the year in the southeast but dry in the southwest and farther inland. A savanna climate, with marked wet and dry seasons, prevails in the north and west, while a steppe climate with little precipitation is found in the far north. In general, the length of the rainy season decreases from south to north. In the south, the rainy season lasts from March to November, whereas in the far north it lasts only from mid- May to September. A marked interruption in the rains occurs during August in the south, resulting in a short dry season often referred to as the “August break.” Precipitation is heavier in the south, especially in the southeast, which receives more than 120 inches (3,000 mm) of rain a year, compared with about 70 inches (1,800 mm) in the southwest. Rainfall decreases progressively away from the coast; the far north receives no more than 20 inches (500 mm) a year.
Temperatures and Humidity
Temperature and humidity remain relatively constant throughout the year in the south, while the seasons vary considerably in the north; during the northern dry season, the daily temperature range becomes great as well. On the coast, the mean monthly maxi- mum temperatures are steady throughout the year, remaining about 90 °F (32 °C) at Lagos and about 91 °F (33 °C) at Port Harcourt; the mean monthly minimum temperatures are approximately 72 °F (22 °C) for Lagos and 68 °F (20 °C) for Port Harcourt. In general, mean maximum temperatures are higher in the north, while mean minimum temperatures are lower. In the northeastern city of Maiduguri, for example, the mean monthly maximum temperature may exceed 100 °F (38 °C) during the hot months of April and May, while in the same season frosts may occur at night. The humidity generally is high in the north, but it falls during the harmattan (the hot, dry northeast trade wind), which blows for more than three months in the north but rarely for more than two weeks along the coast.