This paper presents the results of a study carried out to examine electrical characteristics of high voltage Silicone Rubber (SIR) insulators under weather pollution conditions. The specimens of SIR with and without Alumina tri-hydrate (ATH) filler have been chemically prepared. The AC (50 Hz) surface aging of SIR specimens have been evaluated under salt fog chamber. Furthermore, the relationship between the leakage current and time to failure for SIR specimens with various concentrations of ATH filler under different weather pollution conditions has been measured in this work.