We present a 1-year long representative δ18O record of water vapor (δ18Ov) in Niamey (Niger) using the Wavelength Scanned-Cavity Ring Down Spectroscopy (WS-CRDS). We explore how local and regional atmospheric processes influence δ18Ov variability from seasonal to diurnal scale. At seasonal scale, δ18Ov exhibits a W-shape, associated with the increase of regional convective activity during the monsoon and the intensification of large scale subsidence North of Niamey during dry season. During the monsoon season, δ18Ov records a broad range of intra-seasonal modes in the 25-40-day and 15-25-day bands that could be related to the well-known modes of the West African Monsoon (WAM). Strong δ18Ov modulations are also seen at the synoptic scale (5-9 days) during winter, driven by tropical-extra-tropical teleconnections through the propagation of a baroclinic wave train-like structure and intrusion of air originating from higher altitude and latitude. δ18Ov also reveals a significant diurnal cycle, which reflects mixing process between the boundary layer and the free atmosphere during the dry season, and records the propagation of density currents associated with meso-scale convective systems during the monsoon season.