The plastic deformation processes that occur in a tensily deformed High Density Polyethylene specimen were studied from full-field strain and strain rate measurements obtained by 3D DIC (Digital Image Correlation). The tensile tests were performed every 10 degrees C from room temperature to 120 degrees C. For temperatures below 60 degrees C, it is shown that the strain localization effect becomes less pronounced when the temperature increases. For temperatures higher than 60 degrees C, the material is found to exhibit double yielding behavior. By analyzing the DIC data in Lagrangian representation, it was possible to quantitatively highlight the strain localization effect that is specifically associated with the second yield. The second yield strain (epsilon(Y2)) was measured and appeared to be nearly independent of temperature. For temperatures smaller than 60 degrees C, it was found that the threshold strain corresponding to epsilon(Y2) also marks the onset of the deformation process phase during which the volume strain strongly increases. On the basis of previous WAXS (Wide Angle X-ray Scattering) studies of our research team and on literature we concluded that the critical strain epsilon(Y2) corresponds to the onset of the lamellar morphology destruction. At high strain levels, the neck stabilization phase was shown to proceed according to a strain driven scheme characterized by threshold strains that are temperature-independent. The experimental values of the threshold strain marking the onset of the stabilization phase are found to be in good agreement with those found using the Haward-Thackray model.