This data release contains monthly 270-meter gridded Basin Characterization Model (BCMv8) climate inputs and hydrologic outputs for the Salton Sea Watershed, which crosses the international border into Mexico in the southern part of the basin. Downscaled gridded climate inputs (Daly et al., 2008) for the California portion of the BCM (Flint et al, 2021) include: precipitation (ppt), minimum temperature (tmn), maximum temperature (tmx), and potential evapotranspiration (pet). Historical climate data covering the Mexico portion of the watershed was unavailable. Climate data for the California portion of the watershed was regridded using regression techniques described in Flint & Flint (2012) to extend climate inputs into Mexico. Other model inputs include elevation, soil, land use, geology, and soil thickness data. These data were collected and processed for the Mexico portion of the watershed and merged with the BCM model inputs for the California portion of the watershed. Gridded hydrologic variables include: actual evapotranspiration (aet), climatic water deficit (cwd), snowpack (pck), recharge (rch), runoff (run), and soil storage (str). The units for temperature variables are degrees Celsius, and all other variables are in millimeters. Monthly historical variables from water years 1896 to 2023 are summarized into water year files and long-term average summaries for water years 1981-2010 and 1991-2020. Raster grids are in the the North American Datum 1983 (NAD83) California Teale Albers (meters) projection in an open format ascii text file (*.asc). References cited: Daly, C., Halbleib, M., Smith, J.I., Gibson, W.P., Doggett, M.K., Taylor, G.H., Curtis, J. and Pasteris, P.P., 2008. Physiographically sensitive mapping of climatological temperature and precipitation across the conterminous United States. International Journal of Climatology: a Journal of the Royal Meteorological Society, 28(15), pp.2031-2064.https://doi.org/10.1002/joc.1688 Flint, L.E., Flint, A.L., and Stern, M.A., 2021, The Basin Characterization Model - A monthly regional water balance software package (BCMv8) data release and model archive for hydrologic California (ver. 4.0, May 2024): U.S. Geological Survey data release, https://doi.org/10.5066/P9PT36UI.