On the basis of field observations and modelling of morphodynamic processes, the concept of coastal zone development during the transition of daily average temperatures to minus values was formulated and presented. It has been established that when the temperatures pass to average daily minus values, the active morpholithodynamic phase of the coastal zone development does not stop. Changes in the wave-absorbing properties of the beach during freezing of beach sediments, changes in the profile of the coastal slope during the formation of marginal ice, rearrangements of the underwater coastal slope under the landfast ice by tidal currents determine the character of morpholithodynamics of the shores of tidal cold and subarctic seas. Emphasis is placed on the fact that the most intense scouring occurs in November-January. During this period, beach sediments freeze at the upper levels of the coastal profile, which are wave-absorbing for storm conditions at maximum tides, and their wave-absorbing properties deteriorate as a result. The period of maximum danger of coastal scarp destruction, ending with the formation of ice and landfast ice, was determined. It is concluded that the calculated period of hazardous impacts on the coastal scarp corresponds to field observations and confirms the proposed concept of coastal zone development after the transition of average daily temperatures of beach sediments to minus values.