Long-term annual or seasonal averages of climatic variables like temperature, has generally been used as indicator for the assessment of climate change. Accordingly, this paper is aimed to examine extreme temperature as indicative climatic variable in synoptic stations of Semnan located in Semnan province during a 42 year period (1965-2006) to determine recent climatic changes over the mentioned area. To achieve the aim, 7 indices of extreme temperature recommended by the internationally agreed WMO-CCLICLIV AR list of over 50 climate change indices climate extremes were selected and calculated. The seven indices are consist of cold nights, cold days, warm nights, hot days, summer days, frost days and diurnal temperature range. These indices describe cold extremes as well as warm extremes. Extreme temperature indices for this study are based on time series method and the 1st and 99th percentiles.Results of this research indicated that thermal conditions over the area are changing as shown by a warming trend identified during the study period. Results of this study also showed that the marked negative trends for indices such as cold days, cold nights, frost days and diurnal temperature range over the region. While significant increases are detected in the annual number of hot days, warm nights and summer days.