This tabular data set represents monthly average precipitation values (millimeters) described in Wolock and McCabe (2018), compiled for the NHDPlus version 2 data suite (NHDPlusV2) for the conterminous United States for the years 1945 - 2015. Linkage of the precipitation data with NHDPlusV2 is achieved through the common unique identifier COMID. The precipitation values are estimated both for: 1) individual reach catchments and 2) reach catchments accumulated upstream through the river network. The reach catchment information characterizes data at the local scale, whereas the catchments accumulated through the river network characterize cumulative upstream conditions. The network-accumulated values are derived using two methods: 1) divergence routing and 2) total upstream routing. Both approaches use a modified-routing database (Schwarz and Wieczorek, 2018) to navigate the NHDPlusV2 reach network and to aggregate (accumulate) the metrics derived from the reach catchment scale.