Aging of rubber is dependent on exposed temperature. Temperature of rubber bridge bearings is affected by environmental conditions such as ambient temperature, solar radiation, and wind. In addition to these environmental conditions, a size of rubber bearing affects the bearing temperature. In this study, to examine temperature of rubber bridge bearings exposed to environmental conditions, temperatures of a natural rubber bearing exposed to environmental conditions were measured for six months. Then, a finite element model of a rubber bridge bearing for the heat transfer analysis was developed to match the measured temperature. By performing finite element analysis of rubber bearings with different dimensions under different environmental conditions, an empirical formula to estimate bearing temperature based on solar radiation was proposed.