In this article, we extend our previous study of the pi-pi scattering lengths under the presence of an external magnetic field, including (mite temperature effects. The novelty of this work is precisely the introduction of temperature into the discussion and its interplay with the magnetic field. As in the previous article, we base our analysis in the linear sigma model, and our calculations are exact within this context. Although the effects are comparatively small, it is interesting to remark that the magnetic field and temperature display opposite effects over the scattering lengths.