The main idea of this research depends on defining and mapping the borders of minimum and maximum reference Evapotranspiration (ETo) on a spatial and temporal basis (over the period from 1979 to 2014 in every region in Egypt). Acceptable results could be achieved through using appropriate equation adjusted to local conditions to calculate ETo. These results should help the Egyptian government and policy makers to identify priorities for agricultural land reclamation, where the most important limiting factor in Egypt, for the agricultural sector, is water. Estimation of ETo according to FAO-Penman-Monteith (FPM) method depends on Location, Elevation, Temperature, solar radiation (sun shining hours), relative humidity (RH) and wind speed which are mandatory parameters to calculate ETo. Although the scarcity of climate data is a major problem in most developing countries, the climatic mathematical models are considered as the best solution for none or rare climatic database regions. These models depend on many parameters which can be derived from the remotely sensed data. The modeled data must be evaluated and calibrated with a measured data. The modeled Tmax, Tmin and Rad were validated with measured data with R-2 as high as 0.97, 0.85 and 0.95 respectively. The R-2 between obtained ETo from measured data and the resulted ETo from modeled data was 0.9. The resulted linear equation was used to calibrate the results of ETo from modeled data. Kiriging-spatial-statistics method (KSS) was used to generate spatial surface maps of ETo. Monthly minimum, maximum and mean ETo maps were produced using KSS method.