As of late August, in the core period of the rainy season, West Africa continue to be characterised by variable conditions. Rainfall deficits persist over some areas in the western parts of the region (northern Mali and most of Mauritania) as well as in southern Guinea extending into Sierra Leone. Below average rains are also noticeable over eastern Niger, around Lac Chad, south-eastern Nigeria extending into southern Cameroon and north-eastern CAR. August provided respite and offset early season dryness in most of the Sahel. Due to much improved rainfall since mid-July, above average-to-average rainfall are now widespread in the Sahel region and most of the region except some areas in the eastern parts of the region. The Westernmost areas of the Sahel benefited from more favourable conditions. Heavy rainfall of above 200 mm has affected large areas in Senegal, western central Nigeria, south-western Mali, the western half of Guinea, southern Chad, and western Sierra Leone raising flooding concerns
Overall, the rainy season has so far (between 1 May and 31 August, been characterised by mostly average to above average conditions in the west Africa region. Rainfall deficits mainly affected northern Mauritania. Furthermore, in pockets in central Nigeria, extending south-eastern Nigeria and neighbouring region south-western Cameroon, southern Lac Chad, south-western Guinea, north-eastern Sierra Leone and north-eastern Mali below average rainfall were recorded. Beginning from mid-July, the rainfall situation over the region has improved resulting in a significant decline in the rainfall deficits. The seasonal cumulative rainfall from May 1st to August 31, has been above average over most of the region. However, negative impact of dryness on crop and pasture development over areas where dryness has persisted for a very long time such as northern Senegal, southern Mauritania, northern Nigeria, and Lac Chad is expected. As a result of the continued widespread wetter than average conditions across the region since mid-July, markedly above average vegetation cover extends over much of the Sahel across Mali, north-eastern Burkina Faso, Niger, Chad, far NE Nigeria, north-western Nigeria and northern Senegal. Meanwhile it can be observed low vegetation recovery from some pockets over far western of the region (over southern Mauritania, northern Senegal, central Mali), northern Nigeria and around Lac Chad due to early rainfall deficits.
According to short-term forecasts covering the period until 20 September 2021, average to above average rainfall will be recorded in most of the region in August. The Sahel, the mono river and Gulf of Guinea will likely benefit from more favourable conditions and receive above normal rains. However, northern and western Mauritania, eastern Chad, south-eastern Nigeria, northern and southern Cameroon and CAR will be drier than average.
According to the PRESASS 2021 seasonal forecast June Update, average to above average seasonal rainfall (in June-August 2021) is expected over most of the Sahelian and Sudanian belt, except for the coastal areas of southern Mauritania, Senegal, The Gambia, Guinea Bissau, Guinea and Sierra Leone. These conditions are associated with an early to normal onset of seasonal rains in the western parts of the region (Mauritania, Senegal, Guinea Bissau, Guinea, western Mali and western Burkina Faso), and normal to late in the eastern sector (eastern Burkina Faso, Niger, northern Nigeria and Chad) and long to medium dry spells throughout most of the region. This could mean that the region might be affected by more irregular and extreme rainfall during the 2021 season, with an increased risk of prolonged dry spells affecting crop development, and intense rainfall leading to floods.