Presented are the results from investigating spatio-temporal variability in surface air and soil temperatures at depth across the territory of Western Siberia at the end of the 20th — beginning of the 21st centuries. It is established that there were seasonal differences in temporal changes of climatic parameters in the north and in the south of the region: in the early 21st century, the highest rates of warming were observed in spring throughout the region, whereas the trends were oppositely directed during the winters season in the north and in the south. A comparison is made of the estimates obtained with instrumental observations. It was determined that, in spite of the identified differences in the seasonal behavior of the values of soil temperature trends at different depths, it is more appropriate to use reanalysis data in describing regional climate variability. The identified trends in soil temperature fluctuations at different depths are generally similar to air temperature changes. Examination of soil temperatures in the 28–100 and 100–255 cm layers from the reanalysis dataset showed that, in contrast to the situation for 1979–1998, the time interval 1999–2015 showed a decrease of this value in autumn and winter and its significant decrease during the spring-summer period, with the highest rate in spring in the arctic zone of the territory. It was found that the changes observed according to reanalysis data indicate a rise of temperature in upper soil layers, which, in turn, can lead to an increase in the depth of the layer of seasonal thawing.Keywords: air temperature, soil temperature, spatio-temporal variability, regional climate, permafrost zone.