Design and installation of a good irrigation system require information on soils, crops, climate, water supply and topographical field data. Apart from the climatic and water supply data all the others are somehow constant for specific farms and can be determined through field survey. In many of the developing nations observed meteorological data are often inadequate in terms of length, completeness and spatial coverage. This hinders proper planning of resources utilization. Use of climatic data in planning and determination of irrigation water requirements is one of the feasible criteria, since it ensures sustainability of the projects. This requires among others, long-term weather data records. However, in many areas such data are inadequate in terms of length and completeness. This work explores the possibilty of generating relaible weather data where short-term data is available using stochastic weather generators. This work provides a good guide to irrigation systems' designers.