A finite-range density and momentum-dependent effective interaction is used to calculate the density and temperature dependence of the symmetry energy coefficient C{sub sym}({rho},T) of infinite nuclear matter. This symmetry energy is then used in the local density approximation to evaluate the excitation energy dependence of the symmetry energy coefficient of finite nuclei in a microcanonical formulation that accounts for thermal and expansion effects. The results are in good harmony with the recently reported experimental data from energetic nucleus-nucleus collisions.