  We discuss the thermal behaviour of the pion vector form factors and
calculate them in one-loop Chiral Perturbation Theory. The perturbative result
is used to analyze the $T$-dependent electromagnetic pion charge radius,
obtaining a rough estimate of the deconfinement critical temperature. Imposing
thermal unitarity, we generate the $\rho$ resonance pole for the form factor in
the center of mass frame. The $\rho$ peak height in the modulus of the form
factor decreases for increasing temperature, while its width increases and the
peak position is slightly shifted downwards for $T\simeq$ 150 MeV. These
results point in the direction suggested by many analysis of dilepton
production data in relativistic heavy ion collisions.
