The spatial interpolation of hydrometeorological data aims at estimating the value of rainfall at a given site based on the observation at neighboring stations. This is a problem of operational hydrometeorology that is regularly encountered in the spatial estimation procedures. In this paper, an optimum interpolation method is validated for the analysis of monthly rainfall amounts over Turkey. Hence, a two dimensional statistically optimum interpolation scheme is generated for the analysis of monthly rainfall amounts over Turkey. Monthly spatial correlation functions are used for the analysis and modelling of the spatial monthly rainfall variability.