Drought is a natural climatic phenomenon. However drought characteristics differ between different areas, but it happens in all climatic zones, including arid and humid regions. It is important, therefore, to recognize, assess, analyzes and monitor it in Iran. Sixty two synoptic and climatologic stations were selected in this research based on corrected De Martonne different time scales (5, 7, 9 12 months) and for assessing the effect of data record, it was calculated for 16, 26, 31 36 year periods at the beginning and end of data record. The results show that BMDI is mostly applicable for humid climates but in the arid climates, it could be used just for 5, 7, 9 12 month time scales. All of the indices showed the best potential for using in sub-mediterranean regime. Trend Analysis showed the "beginning 31-years" period to be the best data record, which also was approved by Cluster Analysis. Key words :Drought, Bhalme-Mooley Drought Index, Corrected De Martonne
