A new kinetic model of 13 excited vibrational levels of the H2O molecule has been developed. This model takes into account all vibrational-translational (V-T) and vibrational-vibrational (V-V) processes of the energy exchange at collisions of H2O with N2, O2, and O, which are important under conditions of the middle atmosphere. Different possible values of the rate constants of inelastic collisional processes are analyzed with the allowance made for new experimental data. Thirty-three rovibrational transitions that form the water vapor bands at 1.4, 1.9, 2.7, 3.2, 4.7, and 6.3 mm are considered. Populations are calculated for 13 excited vibrational states of the H2O molecule for daytime in midlatitudes.