Estimation of the daily average of temperature and relative humidity with common methods is the average of the three standard hours (3, 9 and 15) Greenwich Mean Time. The curve of these two variables on a normal day is a skewed curve to the right. Climatic conditions of the meteorological stations are also another parameter to be considered. Daily average of relative humidity patterns shows only half of a daily value. Therefore, the equal coefficients could be used only as approximation for estimating daily average of relative humidity. This research presents a new method for estimating daily average of temperature and relative humidity in Mountainous regions of Iran. The Patterns for the sample stations in each climatic region were presented separately. Therefore, we used from three clustering of Iran and Systematic sampling to select sample stations. The best models were presented by reviewing the required statistics and analyzing the residuals. The coefficient of determination (R2) and the Fisher statistics show that the patterns have a good ability to estimate the daily average of temperature and relative humidity. The mean squares errors are a measure of the applicability of patterns. The accuracy of the estimating daily average of temperature and relative humidity recommended models in Mountainous regions and its sample stations was confirmed by calculating the mean squared errors. Proposed patterns of this study have less error than the common patterns.