NSIDC-0747 contains melt-season indicators that can be used to delineate various stages in the summer melt and freeze-up period of sea ice. The data were primarily derived using Sea Ice Concentration (SIC) observations from the NOAA/NSIDC Climate Data Record of Passive Microwave Sea Ice Concentration (G02202) and the Snow Melt Onset Dates (NSIDC-0105) from SSM/I-SSMIS Brightness Temperatures products. The main parameters for this data set include the dates of melt onset, early melt onset, and continuous melt onset; dates of early and continuous freeze onset; day of opening (last day SIC is above 80%); day of retreat (last day SIC drops below 15%); day of advance (first day SIC increases above 15%); day of closing (first day SIC increases above 80%); total outer ice-free period; total inner ice-free period; seasonal loss-of-ice period; seasonal gain-of-ice period; and the seasonal ice zone. These data are available for 1979 through 2024 and are gridded on the NSIDC northern hemisphere polar stereographic grid at 25 km.