In this study, an assessment of the thermal conditions and a comparative analysis of the urban and suburban surroundings of Sarajevo (SA) and Banja Luka (BL), Bosnia and Herzegovina, were performed. The study covers the period 2001-2020 and uses hourly observations at 0 h, 6 h, 12 h, and 18 h Universal Time Coordinated. Values of modified physiological equivalent temperature (mPET), one of the commonly used indices, were calculated from basic climate data using the RayMan model. The study results indicate higher and more frequent heat stress in the urban compared to the suburban surrounding during the summer and higher and more frequent cold stress in suburban areas. Due to the climatic characteristics of the area, SA has a higher frequency of cold stress categories than BL, while BL has a higher frequency of heat stress categories. Mean daily and monthly mPET values indicate the mPET urban-suburban difference that follows the definition of the urban heat island. The largest differences between urban and suburban areas appear in midday and evening. However, in the warm part of the year, morning mPETs were lower in urban than suburban surroundings, possibly due to the lack of sun at the urban meteorological stations caused by the layout of buildings. The analysis also revealed unexpected differences between urban and suburban values of meteorological elements in certain parts of the day in SA, showing the used urban station in SA is not the most suitable for urban climatological research.