<p>The study of changes in extreme winter events (extreme cold and thaws) in the Lake Baikal region is important for understanding the impact of the transforming winter climate on the unique lake ecosystem and has both scientific and socio–economic significance. Changes in extreme winter events within the calendar winter in the Lake Baikal area in the context of climate warming were analyzed using the minimum daily temperature for the observation period at each station. It was revealed that extreme winter phenomena have undergone a notable transformation, and trends and regional features of these changes were identified. For the first time, the frequency of occurrence of extreme cold and thaws, multiyear distribution, and intra–seasonal variability of these extreme phenomena were investigated. Spatial differences in frequency and variability of extreme frosts and thaws were found. The frequency of extreme cold (T ≤ − 30&#xa0;°C) began to decline in the 1980s, whereas the number of unusually warm winter episodes (thaws, T ≥ 0&#xa0;°C) began to increase in the 1970s. In 1990–2024 in the northern part of the lake basin, the number of extreme cold events decreased by 16%, and thaws increased by 46%. At the same time, the southern part of the basin exhibits the most intense warming, with a 25% drop of extremely cold days and a 50% rise of thaws. The main reasons of changes in extreme winter phenomena and their impact on the lake ecosystem and the socio–economic sectors were considered.</p>