Climate variability, in Africa in general and in the Republic of Congo-Brazzaville in particular, has been widely documented over the past 20 years. However, variables related to rainfall, such as the nine-month rainy seasons, have been very little studied in the Bateke Plateaux zone, which play a major role in regional hydrology. The objective of this study is to investigate the influence of climatic events on seasonal rainfall patterns on the Plateaux Bateke. On the one hand, it involves monitoring the evolution of climatic parameters through the analysis of temperature, relative humidity and rainfall variation. On the other hand, it was a question of comparing the monthly rainfall normals over the period 1987-2016 in order to determine the behaviour of seasonal rainfall patterns in the context of climate variability. The principal component analysis, based on nine (09) variables, highlighted the impact of climate variability on seasonal rainfall patterns. The first principal component (F1) is associated with the factors defining the climatic conditions of the Plateau Bateke. The second main component (F2) does not express clear correlations. Generally speaking, the temperature and relative humidity of the air are factors in the temporal variability of seasonal rainfall regimes on the Plateaux Bateke.