Wireless sensor networks (WSNs) are widely preferred measurement and monitoring tools for a large variety of industrial and environmental applications thanks to their low-cost, energy-efficiency, flexibility, and ease of deployment. However, the use of WSNs for measuring and monitoring industrial applications generating data at high rates, such as online monitoring of partial discharge activities in high voltage equipment in the power grid, presents a significant challenge for the system operators. In such applications, packet arrival rates could increase rapidly due to the occurrence of cascaded faults in the monitored environment. The WSNs with multihop topologies could experience excessive delays and an increase in packet drop of vital data due to the overwhelming increase in the packet arrival rates. Therefore, there should be an optimum operating point of the network where high packet arrival rates and low latency can be maintained at the same time. Thus, there is an immediate need for carefully designed quality of service (QoS) differentiation schemes that can guarantee the delivery of critical data with minimum latency and least loss. In this paper, we present a QoS differentiation scheme for high priority data in multihop WSNs based on an optimization scheme. Analytical and simulation results show that our proposed scheme significantly reduces the delay while maintaining high data delivery ratios and energy efficiency of the network.