Development and accuracy assessment of a 12-digit hydrologic unit code based Real-Time climate database for hydrologic models in the US

•A method was developed to extract the most representative weather for watersheds.•A complete real-time dataset (historical and forecast) was developed at HUC-12 level.•An obvious bias was observed in extreme values in the national forecast data (NFD).•The NFD shows a larger bias in predicting maximum temperature than the minimum.