Long-term temperature conditions of 3,2 m thick soil layer are studied based on the data of Transbaikalian weather stations. Among all the thermal factors, the most informative one, the smallest monthly mean temperature in the annual cycle at the standard measurement depth, is used. Its vertical profiles reflect the depth variations of the temperature and its spatial diversity. They constitute the base for a newly developed graphical classification scheme for wintery thermal conditions of soils. It includes five types of the thermal conditions