Meteorological disasters such as typhoons, forest fires, and floods can damage the communication infrastructures, which will further disable the communication capabilities of cellular networks. The multi-hop wireless communication based on IoT devices (e.g., rescue robots, UAVs, and mobile devices) becomes an available and rapidly deployable communication approach for search and rescue operations. However, Age of Information (AoI), an emerging network performance metric, has not been comprehensively investigated in this multi-hop model. In this paper, we first construct a UAV-relayed wireless network model and formulate the end-to-end instant AoI. Then we derive the optimal location of the relay UAV to achieve the minimum instant AoI by mathematical analysis. Simulations show that the derived relay location can always guarantee the optimal AoI and outperform other schemes.