This work presents an experimental study of copper cathode erosion in magnetically driven arcs as a function of electrode temperature. The experiments were carried out in air at atmospheric pressure. A critical temperature of about 500 - 600K for the transition from micro- to macro- erosion was found for magnetic fields in the range 0.01 - 0.35 T. We show that the electrode temperature is the main parameter that determines erosion, especially in the macro- erosion regime when it strongly increases with temperature. The obtained experimental data can be represented as an exponential function of the time for the electrode surface to reach the fusion temperature underneath the arc root.161SI16