The Neversink River watershed (above the Neversink Reservoir) in the Catskill Mountains of New York, USA has been a focus of U.S. Geological Survey research for decades regarding stream geochemistry, acidification, and ecology dynamics. In 2019, the Water Mission Area Next Generation Water Observing Systems Program (NGWOS) augmented the existing stream gage network to include multiscale instrumentation aimed at characterizing various aspects of groundwater discharge to streams, including the collection of paired air and stream water temperature monitoring stations. Groundwater discharge from hillslopes and underlying aquifers acts as an important component of stream baseflow, and influences stream thermal regimes, creating characteristic signals that can be analyzed to infer baseflow generation process and resiliency. This data release contains input and output files for the spreadsheet-based stream total heat budget model HFLUX (Glose et al., 2017; Briggs et al. 2017). Various scenarios of stream discharge, shading, and groundwater inflow were developed at hourly timescales to explore the physical controls on daily air-water temperature relations. The conceptual scenarios are based on the physical and meteorological conditions of the upper Neversink Reservoir Watershed. The synthetic output data are at 60 min timestep over 5 days with 0.5 m spatial resolution along a 1D, 5 km model stream channel. Simulated stream temperature data are contained in the ‘Output_data’ directory as detailed in the local 'README_output’ textfile. HFLUX input files for each scenario are contained in the 'Input_data' directory. There are subfolders for each scenario, which contain the Excel-based HFLUX input files along with ASCII versions of each spreadsheet input tab, as detailed in the local 'README_input' textfile. Finally, the 'HFLUX' directory contains the model executable files used for this study in .m textfile format and a PDF file describing how they are used. Glose, A. M., Lautz, L. K., and Baker, E. A., 2017, Stream heat budget modeling with HFLUX: Model development, evaluation, and applications across contrasting sites and seasons, Environ. Model. Softw., 92, 213–228, https://doi.org/10.1016/j.envsoft.2017.02.021 Briggs, M.A., Lane, J.W., Snyder, C.D., White, E.A., Johnson, Z.C., Nelms, D.L., Hitt, N.P., 2017c. Modeled temperature data developed for study of shallow mountain bedrock limits seepage-based headwater climate refugia, Shenandoah National Park, Virginia: U.S. Geological Survey Data Release, dx.doi.org/10.5066/F7F47M8Q