This paper presents the rainfall variability along the southern flank of the Bambouto mountain. Data were collected from rain gauges, while spatial variability was estimated through daily recorded data. Monthly and annual data were used to draw isohyetes via the triangular method, with linear interpolations between observation points. Results show that rainfall is highly variable along the slope. Daily rainfall amounts range from 0.1 mm to 120 mm. Mean yearly rainfall is 1918.1 mm. Rainfall amount does not have a linear relationship with altitude. Dschang is characterised by abnormally high rainfall. Following a North-South direction, rainfall decreases from Dschang to a Melang-Loung-Djuttitsa axis. From this axis, the gradient reverses as rainfall increases rapidly towards the Mélétan mountain. The existence of the relatively dry zone within the hillside seems to be due to the influence of two air masses. The first is cold and very wet which moves from the Mamfe basin to the summit zone where it starts to warm up as it flows towards Melang and Loung where temperature increases. The second comes from the south to south-east monsoon which is also impoverished during the ascension to higher altitudes. It is also likely that a third air mass from the dry harmattan is involved depending on the position of the ITCZ.