The present study was conducted to identify suitable tourism periods based on bioclimatic comfort conditions, with the aim of optimizing tourism activity planning in Herat City, Yazd Province. To this end, two well-established bioclimatic indices, namely the Terjung and Olgyay indices, were employed to assess the bioclimatic comfort conditions of the study area. The climatic data used in this study included monthly mean maximum and minimum air temperatures and monthly mean maximum and minimum relative humidity, obtained from the Herat Synoptic Station over a 19-year statistical period (2006–2024). The climatic comfort conditions and tourism potential of the area were evaluated using the Terjung and Olgyay bioclimatic indices based on monthly temperature and relative humidity data. The results obtained from the Terjung index indicated that May and October fall within the range of full thermal comfort (pleasant conditions). June, July, and August are characterized by warm to hot conditions during the daytime, while nighttime conditions during these months, particularly in June, July, and August, fall within the pleasant range. The cold-season months (December, January, February, and March) are characterized by very cool to cold conditions. According to the Olgyay index, May and September exhibit pleasant conditions, whereas June, July, and August are characterized by warm conditions. The cold-season months (December to March) require the provision of thermal energy to achieve comfortable conditions. A comparison of the two indices shows that May and October can be identified as the common periods with favorable climatic conditions for tourism in the study area.