Using numerical model calculations, we investigate the transient heating effect from magnetospheric charged particle precipitation as proposed by Baker et al. (1987). Under extreme circumstances, the transient temperature increase may reach 1 K if the heating duration lasts more than one minute and the energy influx reaches 104 ergs/cm²/s. Otherwise, the expected temperature rise should be substantially smaller (ΔT < 0.05 K). From this point of view, optical observations capable of differentiating various degrees of particle irradiation effect (i.e., modification of optical properties of surface dust layer and/or regolith structure) might be more appropriate to pinpoint signature of Mercury's auroral zones.