Abstract <p>Based on data from the weather station network, this study examines changes in the boundaries of areas unfavorable for agricultural production in European Russia and Western Siberia over the period 1991–2020 and the preceding 30 years, using the Selyaninov hydrothermal coefficient. The extent of these areas is determined from satellite data on the distribution of arable land. In the southern part of the agricultural zone, an arid type of warming during the growing season was associated with a substantial increase in the frequency of severe droughts in May–August and led to an expansion of unfavorable land boundaries. Their area increased by 1.5–2 times in the Southern and North Caucasian federal districts and in the southern part of the Volga Federal District. Already at present, more than a third of arable land in the Southern Federal District can be classified as unfavorable according to climatic characteristics. In the northern part of the agricultural zone, humid-type warming in August–September caused an increase in unfavorable land area due to more frequent years with excessive overwetting. Nearly all CMIP6 climate models were found to simulate a more arid climate in the study region. The expected aridization may lead to further expansion of the area of unfavorable lands in the south and southeast of European Russia and to its reduction in the north of the agricultural zone.</p>