Weather condition is one of the much effective factors in the principle of architecture and urbanization. So in this research long-term trend of effective climate elements in architecture of Darab city including mean of minimum temperature, temperature mean, mean of maximum temperature, minimum relative humidity, maximum relative humidity, relative humidity mean, wind speed and sun hours in monthly and annual scale during period of 1373 to 1390 are surveyed. First of all, climatic element trend was analyzed and modeled. Next, this element effect on the range of climatic comfort is surveyed on the basis of Oleg bioclimatic chart. Pearson correlation method was used for analyzing trend of climatic element and polynomial models were used for modeling of trend behavior. This research shows that temperature elements have significant rising trend at most months of year and wind and humidity elements have significant decreasing trend. Survey of climate comfort condition of Shiraz city shows that they are in daily conditions in only April month and in nightly conditions in July month in the range of comfort condition by using Oleg bioclimatic chart and in the rest days of year, lack of climate comfort conditions are in Shiraz city.Finally,regarding climate elements on architecture, some points are suggested about climatic design principles.