Vol. 129, No. 3 * Pages 241–372 * July - September 2025

The territory of the Mura-Drava-Danube Transboundary BiosphereReserve is large and includes natural and built-up areas that local communities and tourists use during their outdoor work-related or recreational activities. These activities are affected by the outdoor thermal conditions, especially in the age of changing climate. In this paper we investigate micrometeorological and outdoor thermal comfort conditions in different natural and built-up environments at the area of the Bačko Podunavlje Biosphere Reserve. We chose one clear and calm day every month from October 2020 to June 2021, and performed measurements simultaneously at three different locations: settlement, riverside, and lake at midday hours. The results showed that thermal conditions differ between the different built-up and natural areas, and built-up areas tend to experience up to 7% less cold stress during the colder period than the other two sites according to the physiological equivalent temperature (PET) index. On the other hand, built-up area experiences more frequent strong and extreme heat stress during the warmer months. These and more detailed results presented in the paper indicate the most comfortable periods for outdoor activities in different natural or built-up environments.