Bedtime Facts (62/365)

The largest climate zone in Nigeria is tropical savannah (Aw in Köppen's classification)

Nigeria is entirely in the tropics and therefore annual temperature variation is relatively small. However, humidity and rainfall vary a great deal between the summer and the winter months. Two air masses called Maritime Tropican and Continental Tropical take turns dominating the climate of Nigeria. In most of Nigera the Maritime Tropical air mass originating in the Atlantic dominates between March and November whereas the Continental Tropical air mass originating in the Atlantic ocean dominates between December and late February. The greatest difference between the two is in humidity and thus the amount of rainfall during each season.

The cause of the variation is that during the summer in the northern hemisphere the latitude receiving the greatest amount of solar insolation is the tropic of cancer at about 23 degrees. That latitude runs through the Sahara desert. The intense heat results in upward movement of air and a low pressure at ground level. That low pressure causes winds to blow from the Atlantic. The southernmost coastal regions in Nigeria have a tropical monsoon climate (Am) with distinct rainy and dry seasons with very large amounts of rain in the summer and the longest rainy season. The majority of Nigeria's territory has a tropical savannah climate with an arid season and a rainy season. In the winter, the opposite conditions prevail. There is ground level high pressure in the Sahara causing northerly winds to dominate. The very dry northerly wind is called the harmattan. It contains very little moisture and picks up dust as it moves south from the desert. The harmattan can cause the temperature to drop below 20 C in the central parts of the country or even colder in the extreme north.