The dynamics of the soil water potential and soil temperature at different depths during the year was studied. As the object of the investigation we took soddy-podzolic clay loamy weakly gleyed soils of Zelenogradskiy base of Soil Science Institute. The data of soil water and temperature were derived from the automated meteorologic station “VantagePro2”. In conditions of the sustainable state of the other components of the environment, we discovered sharp spasmodic increase of the soil water potential at the passing of temperature values to the range below zero, i.e., in conditions of the phase overpass of the soil solution. All of the types of soil water potential changes (slow and rapid, significant and insignificant) occur due to the changes (decrease or increase) of the water content and soil temperature. For the first time in our country the thermohydrophysical phenomenon of (thermodynamic process) of sharp (at 5-6 times) and rapid (practically immediate) increase of the water potential after the overpass of the temperature over zero from the area of positive values to the negative values is discovered and described. The knowledge of specificities of the dynamics of soil water potential due to the temperature will allow us to plan the terms and norms of watering.