Human thermal comfort is affected by climatic conditions, and its changes can have significant consequences on the health and well-being of society. The aim of this study is to evaluate the temporal changes of the stress index and analyze its consequences on human comfort in Gonbad-Kavous city over a period of 33 years. This study is of a descriptive-analytical type and the required data, including daily climatic variables temperature, relative humidity, and wind speed, were obtained from the synoptic station of this city. After, the stress index was calculated and were classified into its classes. The statistical methods of long-term averaging, decadal review, cumulative assessment, monthly assessment and trend analysis were used to analyze the data. The findings showed that the climatic conditions of the city have low stability during the study period. Although, cool conditions dominate with an average of 129 days, the number of days with real comfort is only 15 days per year. Decadal analysis illustrated that the third decade was the lowest number of comfortable days with 13 days. The cumulative distribution showed 59% of the days are involved in cool conditions, 27% are exposed to heat stress, 1% are related to days with complete lack of thermal comfort, and 13% of the days enjoy optimal comfort. Monthly analysis showed the most agreeable months were Ordibehesht and Mehr (61% totally share). The long-term trend also indicated a weak decreasing trend about 4 days since the beginning of the period in the number of comfortable days, but the explanatory power of this trend is low. Overall, it can be concluded that Gonbad-Kavous faces a serious lack of pleasant days and high variability. This climate pattern can lead to increased thermal stress on residents, psychological stress due to climate fluctuations and create obstacles in planning outdoor activities.