Extreme climate events (droughts, floods, heat waves) are those that are rare both in their intensity and in the frequency of their occurrence. Changes in the occurrence of extreme events can often have far greater detrimental impacts of ecosystems and human societies than a change in average climate conditions. Damage resulting from extreme weather events in Iran already imposes a heavy toll on society that few economics are easily able to absorb. In this study the reliability and behavior of extreme events in Iran by using extreme climate indices software (ECIS) was investigated. The indices were selected from the list of climate change indices recommended by the CLIVAR. The findings revealed that the cold extreme indices such as FD& ID have significant decreasing trends In addition warm extremes indices such as T40, SU show pronounced increasing. Trend of Indices of extremes precipitation such as WD, is increasing. Analyses of the return periods of cold extreme such as FD& ID show the return periods were long and warm extremes were shorter
)