The region of Sub-Saharan Africa from the Sahel of West Africa eastward to western Ethiopia is prone to meningitis epidemics during the dry season. The dry season, extending from approximately January to May, is poorly understood across West Africa where most research has been focused on the monsoon season. This study evaluates the variation of relative humidity across West Africa over 30 dry-seasons (1979 – 2009) using the NASA-MERRA dataset. Relative humidity has been found to be a critical environmental factor indicating the susceptibility of a region to meningitis epidemics. The method of self-organizing maps is employed to characterize the changes in relative humidity patterns over the course of a single dry season as well as over the duration of the 30 years. The results indicate distinct patterns of relative humidity within a given dry season as well as gradual variations from year to year. Potential future applications involve using the results of the SOM evaluation, in combination with past reports of epidemics, to be used in future decisions involving the efforts to prevent of meningitis epidemics.