In this study, the spatial and temporal distribution of precipitation in the Water District of Central – Eastern Greece is investigated for the 42-year period (1968 – 2009) by using monthly mean data from 35 rainfall gauges, with adequate spatial coverage. The basic objective is to infer the pattern of spatial variation of rainfall over the study area based on meteorological observations. The accurate estimation of rainfall’s spatial distribution is needed whenever hydrological modelling is undertaken at the watershed scale for model calibration and validation. By using timeseries analysis and geostatistical methods, the regional and seasonal precipitation change and regime of this region during over 40 years is analyzed. However, this input is subject to uncertainty due to the random nature of rainfall. For all stations, uniformity checking and appropriate completion (where needed) took place and it appears that orography plays significant role as far the amount of rainfall is concerned. The results indicate that high variations in regional rainfall estimation occur in the mountainous areas, while the variance decreases in shadow areas in all seasons. The analysis of rainfall showed that there exists a wide variation in the rainfall amounts with variation from 382.4mm to 1397mm with a significantly decreasing trend.