The California seasonal snowpack is one of the most valuable natural water storage reservoirs in the United States, with 7 of the 10 most productive agricultural counties in the nation depending on irrigation from the annual Sierra Nevada spring runoff. However, many water management agencies throughout the state are nervously anticipating the climatic extremes of the last decade to continue and wondering how such annual extremes will affect seasonal runoff forecast performance. One way to speculate as to what the future may hold is to examine how basins have responded to extreme conditions of the recent past using climate reanalysis datasets and measured runoff. Here, we leverage an hourly, 4-km reanalysis product that synthesizes multiple large-scale observational and analysis datasets – known as the Analysis of Record for Calibration (AORC) developed by the National Oceanic and Atmospheric Administration (NOAA) Office of Water Prediction (OWP) – to quantify the evolving hydrologic responses to changing climatic conditions. The AORC provides the data necessary to derive hourly, distributed storm precipitation phase – with subsequent hourly rain-snow transition elevations and gridded snowfall fraction of precipitation – and seasonal runoff efficiencies in 14 of the largest Sierra Nevada basins that flow toward the Central Valley from 1980 to 2022. The long-term trends and relationships between these three metrics will provide California water management agencies with crucial information relating to how individual basins respond to changing conditions and climatic extremes.