The paper presents the findings of characteristics of atmospheric circulation and extreme floods in the Baikal region in July 2001. During the flood in July 2001, precipitation at the meteorological stations of the study area was significantly higher than normal. In July, the Inga station reported an impressive maximum precipitation of 311 mm, a remarkable 278% of the long-term average for the month. Historical maximums of daily precipitation were recorded at four meteorological stations. A comprehensive synoptic analysis was conducted to identify the main causes of the extremely high precipitation values that caused a rise in water levels on the left-bank tributaries of the Angara, the upper Lena, and on the rivers of South Baikal in July 2001. Synoptic processes were classified according to the Jenkinson and Collison weather types. For July 2001, eight weather types were identified, two of which – cyclonic and advective types with northern components – emerged prominently during the flood period. The directions of air mass transfer were determined based on the analysis of five-day backward trajectories of HYSPLIT. The following were found to be the primary determinants of the devastating flood’s intensity: (1) active process of southern cyclogenesis; (2) development of blocking processes; (3) high content of precipitable water content over the study area.