| Country | Period | Trend (mm/yr) |
| Benin | No trend | - |
| Burkina Faso | 1901-1969 | −0.57 |
| 1970-2013 | 1.94 | |
| Côte d’Ivoire | 1901-1906 | −27.04 |
| 1907-1913 | 22.64 | |
| 1914-1969 | 0.84 | |
| 1970-2013 | −0.31 | |
| Ghana | 1901-1968 | 1.84 |
| 1969-2013 | −1.42 | |
| Guinea | 1901-1969 | −2.38 |
| 1970-2013 | −0.29 | |
| Liberia | 1901-1969 | −5.04 |
| 1970-2013 | −1.03 | |
| Mali | 1901-1969 | −0.12 |
| 1970-2013 | 0.74 | |
| Mauritania | 1901-1906 | 23.83 |
| 1907-1969 | −0.12 | |
| 1970-2013 | 0.56 | |
| Nigeria | 1901-1903 | 11.88 |
| 1904-1981 | −0.27 | |
| 1982-1987 | 1.18 | |
| 1988-2013 | 0.08 | |
| Niger | 1901-1903 | −1.33 |
| 1904-1909 | 6.67 | |
| 1910-1915 | −7.81 | |
| 1916-1967 | 0.59 | |
| 1968-2013 | 0.97 | |
| Senegal | 1901-1967 | 1.62 |
| 1968-2013 | 1.13 | |
| Togo | No trend | No trend |