To investigate the temperature distribution on the surface of a silicone rubber exposed to partial arc discharges, numerical analyses on thermal characteristics were carried out. The preliminary calculations indicated that there was no dependence of mesh and time step. The temperature on the specimen surface became high in the middle of the discharge gap while those at points of contact between an arc discharge and tips of glass-filter paper used as electrodes became low. The thermal diffusion from the points of contact between the arc discharge and the tips of glass-filter paper into electrolyte electrodes caused the temperature decrease at such points. Copyright © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.