The objective of this paper is to assess the bioclimatic conditions in Serbia during summer in order to identify biothermal heat hazard. Special emphasis is placed on the bioclimatic index UTCI (Universal Thermal Climate Index), whose purpose is to evaluate the degree of thermal stress that the human body is exposed to. For this research, mean daily and hourly (07:00 and 14:00 CET) meteorological data from three weather stations (Zlatibor, Novi Sad and Niš) have been collected for the period from 1998 to 2017. In order to identify patterns of biothermal heat stress conditions, the thresholds of the daily UTCI (UTCI ≥38 ^∘C, referred to as very strong heat stress, VSHS) at 14:00 CET are compared with the thresholds of daily maximum air temperature ($t_{max}\ge \mathrm{35}$ ^∘C, referred to as hot days, HDs), which are further termed as heat wave events (HWEs). The findings show that the UTCI heat stress category “very strong heat stress“ at 14:00 CET indicates heat waves. The most extreme heat wave events occurred in 2007, 2012, 2015 and 2017. Moreover, three HWEs at Niš that occurred in July 2007 lasted 3, 10 and 4 d. HWEs and very strong heat stress events (VSHSEs) recorded in July 2007 (lasted 10 d each), 2012 (lasted 9 and 12 d) and 2015 (lasted 7 and 10 d) were of the longest duration and are considered to be the indicators of biothermal heat hazard. The daily UTCI_14 h heat stress becomes more extreme in terms of severity and heat wave duration up to very strong heat stress.

The bioclimatic analysis of the central area of the city of Niš conducted in this paper is based on the use of the bioclimatic index Humidex, which represents subjective outdoor temperature that one feels in warm and humid environment. The purpose of this research is to observe the index change on a daily basis during the hottest part of the year (June, July, and August) over the period from 1998 to 2017. For the purposes of this analysis, hourly (7:00, 14:00), maximum and mean daily values of meteorological parameters (air temperature and relative humidity) were used, for the period of 20 years (1998-2017), which were measured at Niš weather station (43°19'N, 21°53'E, at an altitude of 202 meters). The findings indicate a gradual change in the bioclimatic characteristics of this area during this period, especially over the last decade. After 2007 there has been a decrease in the total number of the days described as “comfortable”. However, there has been an increase in the index values in all the other heat stress categories characterized by a higher or lower degree of thermal discomfort. The years 1998, 2000, 2003, 2007, 2011, 2016, 2015, and 2017 stand out as adverse years. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 47007, Grant no. 176017, and Grant no. 176008]

The main objective of this paper is to study the outdoor thermal comfort of the central urban zone of Belgrade during summer season in order to examine how different bioclimatic conditions affect human body. For this purposes Humidex, a simple heat index was applied. The research involved analyzing different Humidex values, the so-called “sub-indices” calculated based on hourly (7:00 and 14:00), mean daily and maximum values of meteorological parameters (air temperature and humidity) that were recorded at the meteorological station Belgrade - Vračar.), for the period 1999-2018. Outdoor thermal comfort in Belgrade is generally more adverse in July and August, resulting in most days belonging to the categories of “some discomfort” (30-39) and “great discomfort” (40-44), with periodic recording of the most severe categories of heat stress, as a category “very dangerous”(Humidex>55). Category of “very dangerous” heat stress shows linear increase during July, with positive trend of 0.03 days/10 years. The findings also show that from 1999 to 2018, mean index value gradually rose and values of sub-indices Humidex14h and HumidexTmax have exceeded thresholds 40 for great discomfort and 45 for dangerous heat stress more often then in the previous decades.

The paper presents geoecological evaluation of the city of Loznica for the purposes of sports and recreational tourism based on quantitative method of diversity, V-Wert Method. Using the GIS tool by the quantitative method, the criteria of natural components (relief, forest, water surface and climate) are evaluated for the analyzed area. In the proposed method, the climate factor was supplemented by the analysis of the bioclimatic index Universal Thermal Climate Index (UTCI). When the evaluation was completed, the final results were obtained based on which the degrees of convenience of different parts of the analyzed area have been presented. Out of the total analyzed surface, which amounts to 705 km2, favorable surfaces comprise 21 km2 (2.98%), and very favorable surfaces comprise 33 km2, i.e. 4.68% of the territory. The largest area consists of conditionally favorable terrains - 333 km2 (47.23%). Since one of the basic strategic priorities of the City of Loznica is improvement and development of sports and recreational tourism, the aim of this analysis is to emphasize the potential of the mentioned area in terms of general suitability of the terrain for the development of this type of tourism.

Thermal comfort assessments at local or micro-scales within urban areas can provide crucial insights for the urban adaptation strategies pertaining to climate-conscious urban planning and public health. However, the availability of long-term or mid-term daily or hourly meteorological data sets from urban environments remains a significant challenge even in the 21st century. Consequently, this study aimed to assess the thermal conditions in cities across the western part of the Balkan Peninsula, encompassing five countries (Slovenia, Croatia, Serbia, Bosnia and Herzegovina, and Montenegro), by utilizing the Physiological Equivalent Temperature (PET) index. Meteorological data sets, comprising air temperature, relative humidity, wind speed, and cloudiness, were collected from 32 national meteorological stations/measurement locations spanning the period from 2001 to 2020. The PET calculations were conducted based on meteorological data measured three times per day (7 a.m., 2 p.m., and 9 p.m.). Upon conducting a spatial analysis of the meteorological stations, it was observed that most of them (25 stations) were situated within built-up areas or urban suburbs, rendering them highly relevant for local or micro-scale climate and bioclimate assessments. The findings revealed that urban locations exhibited slightly higher PET heat stress levels, particularly during the summer season and at 2 p.m. Moreover, higher average PET values were observed in both urban and non-urban stations situated within a continental climate during warmer periods, such as summer. In contrast, during the colder seasons, namely winter and spring, higher PET values were prevalent in the Mediterranean region. Furthermore, the PET frequency analysis revealed a greater prevalence of extreme and severe heat stress levels in stations within continental climates, particularly those located in urban areas, as compared to stations in Mediterranean climates. In contrast, during the winter and spring seasons, monitoring stations in close proximity to the Adriatic Sea, characterized by a Mediterranean climate, exhibited significantly lower levels of cold stress compared to inland stations. Evidently, in addition to the climatic characteristics and surrounding terrain, the urban morphology significantly impacts the thermal conditions within cities.

Increasing thermal risk in cities is endangering the health and well-being of urban population and is driven by climate change and intensive urbanization. Therefore, if we plan to enlarge the capacities of cities to be more climate resilient in the 21st century, more detailed monitoring of urban climate on local and micro scales is needed. For this research we performed two microclimate measurement campaigns in urban area of Belgrade, during hot summer days in 2021. In total, five measurement sites were chosen in different urban designs and different local climate zones (LCZs). For thermal monitoring (air temperature – Ta and globe temperature – Tg) the Kestrel heat stress tracker sensor with 1-min measurement resolution was used, but we used 10-min average values. Obtained results showed distinct thermal differences (up to 7 °C on average) between densely built-up areas and green areas. Differences between built-up LCZs are lower with values from 2 to 4 °C. Important part of this research was microclimate monitoring on sites within the same LCZ (intra-LCZ variability). Results showed that shadows and short- and longwave radiation play a paramount role in thermal variability. Direct and reflected radiations on one measurement site increased Ta up to 6 °C and Tg up to 12 °C when compared to other measurement site (in a similar urban design), which was in the shadow.