If using the dataset, please cite as: Guirguis, K., A. Gershunov, B. Hatchett, T. Shulgina, M.J. DeFlorio, A.C. Subramanian, J. Guzman-Morales, R. Aguilera, R. Clemesha, T.W. Corringham, L. Delle Monache, D. Reynolds, A.Tardy, I. Small, and F.M. Ralph. (2022) Historical Catalog of Observed Winter Weather Regimes Impacting California. UC San Diego Library Digital Collections. https://doi.org/10.6075/J089161B The citation for the primary publication associated with this dataset is: Guirguis, K., A. Gershunov, B. Hatchett, T. Shulgina, M.J. DeFlorio, A.C. Subramanian, J. Guzman-Morales, R. Aguilera, R. Clemesha, T.W. Corringham, L. Delle Monache, D. Reynolds, A.Tardy, I. Small, and F.M. Ralph (2022) Winter wet–dry weather patterns driving atmospheric rivers and Santa Ana winds provide evidence for increasing wildfire hazard in California. Climate Dynamics. https://doi.org/10.1007/s00382-022-06361-7 Corresponding author: Kristen Guirguis, kguirguis@ucsd.edu Description of contents: This dataset contains a historical catalog of observed daily atmospheric weather patterns over western North America during November-February, classified according to sixteen reoccurring weather regimes as in Guirguis et al. (2022). These weather regimes have been identified as important drivers of atmospheric river landfalls, Santa Ana winds, floods, and wildfires in California. Details for each item: • Figure 1 shows composites of 500 mb geopotential height anomalies for each of the sixteen weather regimes identified and described in Guirguis et al. (2022). The sample size of each weather regime (n) is given in the title as a percentage of days in the historical record classified within a given weather regime category. • The .csv data file gives the observed winter weather regime classification for each day in the historical record spanning Nov-Feb 1948-2017. Figure 1 can be recreated using the catalog by compositing 500 mb geopotential height anomalies for days sharing a common weather regime classification (e.g., column 4 of the .csv file). Column headers are year, month, day, and weather regime category. Methods: The weather regimes were classified based on sixteen different phase combinations of four North Pacific teleconnection patterns called the “NP4 modes” (Guirguis et al. 2020), which have been identified as important drivers of weather variability over California and western North America (Guirguis et al. 2018, 2020, 2022). The data source is 500 mb geopotential height fields from the NCEP/NCAR global reanalysis (Kalnay et al. 1996), where anomalies were calculated relative to the annual and semiannual seasonal cycle. Additional details are provided in Guirguis et al. (2022).