The development of a warm phase in the climate since the middle of the last century and the improvement of conservation measures have led to the northward expansion of a large number of bird species originally distributed in the southern parts of the Palaearctic. The dispersal of the great egret in Europe is a vivid illustration of this process. Throughout the last century, only rare records of single birds in Russia’s Northwest were known. At the beginning of this century, the breeding range of the species in the eastern Baltic States and Belarus came close to the borders of the region. Based both on original data and on analysis of scientific sources, the process of great egret invasion into Pskov, Leningrad, Novgorod, and Tver oblasts and the Republic of Karelia, the status change from a rare stray to a common vagrant , as well as the formation of the first great egret breeding colonies in Pskov and Leningrad oblasts are considered in detail. Features of the phenology of the species and the spatial distribution of its nesting settlements are given. An analysis of the climatic factors limiting the summer residence zone of the species is also presented.