This data release documents spatiotemporal water-quality, landscape, and climatic conditions in Fairfax County, Virginia from 2007 through 2018. These data were used to evaluate the water-quality and ecological condition of 20 Fairfax County watersheds monitored since 2007. Data include measures of water-quality, precipitation, air temperature, land use, land cover, wastewater and stormwater infrastructure, soil properties, geologic setting, and stream networks. Annual values from 2007 through 2018 are reported for data expected to change over time. Watershed-specific values are reported for data that differ across the landscape. Annual values for the 20 study watersheds and Fairfax County are reported in the file "Spatiotemporal Predictors.csv". A description of each spatiotemporal variable, including data sources, are provided in the file "Data Dictionary.csv".