Abstract Energy excitations in ferromagnets are studied in case a temperature gradient is coupled to the local magnetization. Due to different time scales only the coupling between the spatially varying part of the temperature field and the magnetization is relevant. The magnetothermal coupling with a definite sign breaks the time inversion symmetry and lead to damped spin waves. Applying the model to nanowires it is demonstrated that the energy spectrum is significantly affected by the boundary conditions as well as the initial temperature distribution. The magnetothermal coupling is several orders of magnitude stronger for open wires compared to isolated ones.