The semiarid sahelian zone, or Sahel, forms a belt about 500 kilometers wide that runs from Lac and Chari-Baguirmi prefectures eastward through Guéra, Ouaddaï, and northern Salamat prefectures to the Sudanese frontier. The climate in this transition zone between the desert and the southern soudanian zone is divided into a rainy season (from June to early September) and a dry period (from October to May). In the northern Sahel, thorny shrubs and acacia trees grow wild, while date palms, cereals, and garden crops are raised in scattered oases. Outside these settlements, nomads tend their flocks during the rainy season, moving southward as forage and surface water disappear with the onset of the dry part of the year. The central Sahel is characterized by drought-resistant grasses and small woods. Rainfall is more abundant there than in the Saharan region. For example, N'Djamena records a maximum annual average rainfall of 580 millimeters, while Ouaddaï Prefecture receives just a bit less. During the hot season, in April and May, maximum temperatures frequently rise above 40°C. In the southern part of the Sahel, rainfall is sufficient to permit crop production on unirrigated land, and millet and sorghum are grown (see Agriculture , ch. 3). Agriculture is also common in the marshlands east of Lake Chad and near swamps or wells. Many farmers in the region combine subsistence agriculture with the raising of cattle, sheep, goats, and poultry.
Data as of December 1988