  Corrections of order $T^4$ to vector and axial current correlators in QCD at
a finite temperature $T<T_c$ are obtained using dispersion relations for the
amplitudes of deep inelastic scattering on pions. Their relation with the
operator product expansion is presented. An interpretation of the results in
terms of $T$-dependent meson masses is given: masses of $\rho$ and $a_1$ start
to move with temperature in order $T^4$.
