  In this article we explore the thermal evolution of the $\pi$-$\pi$
scattering lengths in the frame of the linear sigma model. We compute, using
thermofield dynamics, all the one loop diagrams that contribute to $\pi$-$\pi$
scattering. We restrict ourselves to temperature correction only in the pion
sector, due to the Boltzmann supression for the sigma meson. From this analysis
we obtain the thermal behavior of $a_0^0$ and $a_0^2$, s-waves scattering
lengths in the isospin channel I=0 and I=2 respectively. It turns out that
$a_0^0$ grows whereas $a_0^2$ diminishes as function of temperature. We compare
our results with other determinations of the thermal behavior of these
magnitudes.
