While it is well-known that urban temperatures tend to be higher than temperatures of the rural surroundings (namely, urban and rural temperatures have different mean values, a phenomenon called the urban heat island effect), it remains unclear whether urban and rural temperatures exhibit any significant differences in terms of variability and persistence. Moreover, whether urban-rural differences in temperature variability and persistence, if exist, contribute to more heat wave occurrence in urban areas has not been investigated. In this study, we aim to address these two questions using a combination of numerical modeling and experimental data, with a focus on the summer season and the daily scale. Our results show that the urban and rural temperatures exhibit large difference in the mean (as expected) but nearly no difference in the variability, with some difference in the persistence in certain regions. The mean urban heat island effect (i.e., the higher mean urban temperature) contributes to more heat wave occurrence in urban areas, and such impact is strongly modulated by the temperature variability. The urban-rural difference in temperature persistence makes a generally small contribution to the urban-rural difference of heat wave occurrence, with strong regional variabilities. Overall, the more heat wave occurrence in urban environments is to a large extent induced by the mean urban heat island effect.