The Lake Chad Basin embraces a great range of tropical climates from north to south, although most of these climates tend to be dry. Apart from the far north, most regions are characterized by a cycle of alternating rainy and dry seasons. In any given year, the duration of each season is determined largely by the positions of two great air masses--a maritime mass over the Atlantic Ocean to the southwest and a much drier continental mass. During the rainy season, winds from the southwest push the moister maritime system north over the African continent where it meets and slips under the continental mass along a front called the "intertropical convergence zone". At the height of the rainy season, the front may reach as far as Kanem Prefecture. By the middle of the dry season, the intertropical convergence zone moves south of Chad, taking the rain with it. This weather system contributes to the formation of three major regions of climate and vegetation.
Data as of December 1988