Relative humidity data was obtained from the Earth System Research Laboratory (ESRL, http://www.esrl.noaa. gov/psd/data/timeseries/) covering a period 1948 – 2014 on monthly time step. The mean monthly relative humidity for each sub-basin is presented here, which indicates that the equatorial lakes region has relatively high values with very little variation across the months compared to the eastern Nile and main Nile.