In recent years, interest in climatic extreme events (droughts, floods and heat waves) has been growing not only due to their direct impact on many socio-economic sectors, but also as climate change indicators. In this study, the behavior of extreme events is investigated using Extreme Climate Index Software (ECIS) package. The trend analysis of extreme indices is applied to daily series of temperature and precipitation observations from 16 synoptic stations over Iran in the period 1951-2003. Results show that the number of very warm days (T40) has increased while the number of very cool days (ID) has decreased and so the return period (?ret) of cold extreme indices increased and the Tret of warm extreme indices decreased. Changes in total and extreme precipitation indices vary, depending upon geographic location. Symmetric warming in the tails of most indices is seen overall. On the basis of a systematic analysis of observed changes in indices of climate extremes, a significant proportion of Iran is increasingly affected by a significant change in extreme indices in the ~50-yr study period.
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