The soil has the potential to serve as a cooling source for buildings. However, the unavailability of data concerning the thermal behavior of the ground limited the widespread of underground cooling systems. These last years, the concept started to obtain an attention because of the results of some studies indicating that the development of such systems could present an alternative for the cooling and the natural ventilation of buildings. Coupling solar chimneys with buried cooling ducts was investigated as a method of appropriate design for cooling and natural ventilation in hot climates. The modeling of the proposed device was developed and presented in a previous scientific meeting. The value of the ground temperature was assumed. In this work, a method of evaluation of the ground temperature according to the depth and the treatment of the ground surface is presented. In addition, the work intends to show the importance of the potential of the thermal mass of the ground for cooling buildings. The method is estimated on the basis of weather data. The results of this study indicate that if irrigation is applied to the soil surface in summer the ground offers a good source of cooling for buildings. A decrease in temperature to 18°c was noted between the soil temperature at a depth of 1m and the ambient outside temperature.