A simple mean-field description of frustrated antiferromagnets on hexagonal lattices, aimed to describe the high-temperature part of the temperature-magnetic field phase diagram, is proposed. It is shown that an interplay between modulation vector symmetry, Zeeman energy, and magnetodipolar interaction leads to stabilization of the triple-Q skyrmion lattice in a certain region of the phase diagram. The corresponding analytical expressions for phase boundaries are derived. The possible relevance to the high-temperature part of the Gd2PdSi3 phase diagram is discussed.