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Drought is the main causes of significant water imbalance, increase of crop losses or limitation in water consumption, and finally large number of socioeconomic and environmental problems. Precipitation amount is the most important climatic variables that its spatiotemporal variability has a great influence on water resources availability along with the effects of climate change. The Angot index is an indicator to determine the climatic cycles of precipitation as the ratio between the average values of multiannual precipitation over wet and dry periods which highlights the climate significance of monthly precipitation to detect dry or rainy intervals. The aim of this study is to assess and calculation of the Angot inxed in analysis of dry and wet periods of monthly rainfall in rain gauge stations of Ardabil province. The maximum values of Angot index were observed in November and May months. The results proved the suitability of the Angor index in determining wet and dry months and the comparison of the employed index with other common drought indices (e.g. Standardized Precipitation Index) and also different climatic zones of Iran needs further investigations.