Vol. 129, No. 4 * Pages 373–484 * October - December 2025

To better understand outdoor thermal comfort on both seasonal and monthly levels, the current trends and anomalies in the Podrinje-Valjevo Region (PVR) over the past 30 years (1991–2020) and their impact on tourist activities, two bioclimatic indices, the Universal Thermal Climate Index (UTCI) and the Tourism Climatic Index (TCI), were utilized for the temporal assessment of bioclimatic conditions in Loznica and Valjevo. The results show that spring and autumn are the most favorable seasons for outdoor tourism activities, with April, May, September, and October being particularly optimal. According to UTCI, November has also become more bioclimatically favorable due to a rise in average monthly UTCI values. Additionally, UTCI data reveal a notable upward trend in seasonal anomalies, especially during autumn and spring, with average seasonal UTCI values increasing. Although TCI indicates that summer is particularly ideal for tourist outdoor activities and tourists’ thermal comfort, UTCI highlights that summer months can cause significant thermal discomfort due to moderate heat stress. The results obtained can serve to more effective tourism planning in the Podrinje-Valjevo Region in Serbia.