Long-term historical weather data are needed to conduct crop simulation analysis. Simulated climatic data may be used when long series of historic data are not available or convenient or when future data are needed. The aim of this study was to generate daily weather values for maximum and minimum air temperatures, and solar radiation. A number of weather generators and some another stochastic methods are compared here. Data from sixteen stations in Iran with long-term complete weather records were used to compare actual with generated data sets. Result was evaluted by comparing the cumulative distribution function (CDF) of generated and actual values. Correlation coefficiants between values calculated and measured data and errors, were computed. The following informative layers were compiled in GIS system: (1) The error layer of each case, (2) the climatological clasiffication layer, and (3) the digital elevation model (DEM) of Iran. Then using overlapping the diffrent layers, the relationship between climate and high with the error of each method was defined and the best method for generating meteorological data in each area was resulted.