The impact of climatic conditions on human beings can be assessed using bioclimatic indices. In this study, the Universal Thermal Climate Index (UTCI) was applied to assess the bioclimate in Russia. Seasonal features, region-specific features, and extreme values of the UTCI were considered in the climatic conditions of 2001–2015. The UTCI values for the datasets were obtained in the daytime (at 15:00) and at night (at 03:00) in the territory of Russia using the software package BioKlima 2.6. Daily current meteorological data were used as input for the calculations, including air temperature, relative humidity, wind speed, and total cloud cover. It was established that all categories of cold stress and almost all categories of heat stress are observed in Russia, but the cold stress conditions prevail. In winter, cold stress of various categories predominated over almost the entire territory in both the daytime and at night. In summer, conditions of no heat stress and comfort were observed in the largest part of Russia, while conditions of moderate heat stress were noted in the south of the European part during daytime hours. Extreme cold stress occurred over almost the entire territory of Russia with the exception of the west border, the foothills of the Caucasus and the coasts of the Black and Caspian Seas. In the largest part of the country, the maximum UTCI values for the study period corresponded to slight and strong heat stress.