Dynamic Voltage and Frequency Scaling (DVFS) is a widely used methodology to reduce the power consumption of mobile devices. This scheme performs frequency scaling in accordance with a specific governor and sets an operating voltage to be paired with the frequency. Temperature is one of the critical parameters affecting device operation. Practically, a guard-band exists in the operating voltage to ensure safe processor operation even at the worst temperature. DVFS can be optimized in terms of operating voltage under nominal conditions. In this paper, we propose a Temperature-aware DVS (T-DVS) that aggressively reduces the voltage guard-band. We explore the opportunity of providing the minimum operating voltages for frequencies at different temperatures and realize a dynamic voltage control scheme to optimize power consumption. The effectiveness of T-DVS is validated under various thermal conditions by using multi-core application processor. We experimentally observe that T-DVS leads to voltage gain without performance degradation regardless of both thermal conditions and chip characteristics. We show by using off-the-shelf smartphones that the voltage gain achieved by the scheme results in battery lifetime increment.