This paper aims to investigate the transient behavior of a salinity gradient solar pond (SGSP) under Mediterranean climate. For this purpose, a 2D numerical model is developed in which the absorption of solar radiation by different layers of saline water, the wind effect at the SGSP free surface, the heat losses from the SGSP free surface, and the development of the double-diffusive convection in the lower and upper convective zones are considered. The governing equations of continuity, momentum, thermal energy, and diffusion are solved using the finite volume method with SIMPLE algorithm. The validity of the numerical model developed in fortran 95 programing language is achieved through the comparisons of the results computed with the available numerical and experimental results obtained by literature studies. Results show that the developed numerical model can predict transient behavior of the SGSPs with a good accuracy. As an application of this model, the temperature, salt concentration, energy stored, and storage efficiency variations of a proposed SGSP are analyzed under Mediterranean climate. The results show that the lower convective zone (LCZ) temperature increases from 15 °C to around 95 °C whereas the temperature of the upper convective zone (UCZ) varies sinusoidally depending on that of the ambient air. Furthermore, the salt concentration of the LCZ decreases from 250 kg/m3 to around 248 kg/m3 while that of the UCZ increases from 50 kg/m3 to about 52 kg/m3. Additionally, the thermal energy stored is around 135 MJ with an efficiency of about 38%, which confirms the capacity of the SGSP to store thermal energy as sensible heat.