This study evaluates the tourism potential of the Central Plateau of Iran with emphasis on heat and cold stress conditions using the Physiological Equivalent Temperature (PET) index. PET is a widely used human-biometeorological index based on the human energy balance and expresses the thermal environment as an equivalent air temperature perceived by the human body. PET was calculated and analyzed at monthly, seasonal, annual, and regional scales. The required meteorological variables included air temperature, relative humidity, vapor pressure, wind speed, and cloud cover.

Linear regression analysis and the coefficient of determination (R2) were calculated at monthly, seasonal, and annual scales. The results indicated a negative linear relationship between PET and elevation in all months and seasons, meaning that PET values decrease as elevation increases. This confirms the moderating role of altitude, particularly in reducing heat stress. The strongest relationships were observed in spring, especially in March, April, and May, when R2 values approached 0.70. This suggests that elevation plays an important role during the transition from cold to warm conditions. In contrast, the weakest relationship occurred in winter, indicating that other atmospheric factors may become more influential.

In winter, most parts of the region were dominated by cold stress, especially higher-elevation areas, reducing the suitability of outdoor tourism. Nevertheless, warmer lowland areas may provide favorable conditions for winter tourism. In spring, PET values increased gradually, and extensive parts of the region shifted toward thermal comfort or slight heat stress classes. This season represents one of the most favorable tourism periods, because thermal conditions are comfortable and spatial diversity allows flexible destination selection. In summer, PET reached its highest values, and moderate to strong heat stress became dominant, particularly in low-elevation, eastern, and southeastern areas. These conditions limit outdoor tourism and highlight the importance of high-elevation areas as climatic refuges. In autumn, PET values decreased again, and many areas returned to comfort or slight thermal stress, making autumn another suitable tourism season.

The classification of PET values into thermal stress categories confirmed the seasonal contrast in tourism potential. Spring and autumn showed the highest shares of no thermal stress, slight cold stress, and slight heat stress, indicating favorable conditions for outdoor recreation and tourism. In contrast, winter was mainly dominated by moderate to extreme cold stress, while summer was characterized by moderate and strong heat stress. Regional analysis revealed significant spatial heterogeneity. Region 1, corresponding to Kerman, showed more stable and favorable thermal conditions, with frequent comfort and slightly warm classes and limited extreme heat stress. Region 2, corresponding to Yazd, displayed greater thermal variability and therefore requires careful seasonal planning. Region 3, corresponding to Isfahan, was more affected by cold stress, while Region 4, corresponding to Fars, showed an intermediate but heat-prone pattern with mild winters and higher summer heat stress. Overall, tourism development should be based on regional bioclimatic zoning, seasonal tourism calendars, the use of high-elevation areas, and infrastructure adapted to climatic extremes. Such planning can improve tourist comfort, reduce thermal health risks, and support sustainable climate-sensitive tourism.