Regional snowfall index

The regional snowfall index (RSI) is a scale used by NOAA to assess the societal impact of winter storms in the eastern two-thirds of the United States and classify them into one of six categories.

The NCDC has retroactively assigned RSI values to almost 600 historical storms that have occurred since 1900.

The impact of the storms is assessed in six different regions of the United States: the Northeast, Northern Rockies and Plains, Ohio Valley, South, Southeast, and Upper Midwest.

[2] The index makes use of population and regional differences to assess the impact of snowfall.

The baseline area and population represent the average area and population for large storms, so that each of these eight different measures will average to an RSI value of 1.0 among storms considered notable (for the calibration sample).