The regional snowfall index (RSI) is a system used by NOAA to assess the societal impact of winter storms in the United States. The system is a replacement for the Northeast snowfall impact scale (NESIS) system. Since its initiation, the NCDC has retroactively assigned RSI values to over 500 historical storms since 1900.

Storms are ranked from category 0 ("nuisance") to 5 ("extreme") on the scale. The impact of the storms is assessed in six different regions of the United States: Northeast, Northern Rockies & Plains, Ohio Valley, South, Southeast, and Upper Midwest. A category 5 extreme ranking is indicated by a numerical score of 18 or higher on the scale.

Out of the over 500 historical storms assessed since 1900, only 27 storms have been given a category 5 ranking. The highest ranking storm on the list is the Great Blizzard of 1978, which scored a value of 39.07. The most recent storm to receive a category 5 ranking is the March 2026 North American blizzard, which scored a value of 26.97. The following list orders the storms chronologically.

List of category 5 events Year Date Max. RSI Region Ref(s) 20.84 Northern Rockies and Plains 31.89 South 18.53 Southeast 24.42 Southeast 34.20 Northern Rockies and Plains 21.13 South 18.14 Southeast 21.14 Northern Rockies and Plains 34.69 Ohio Valley 20.38 Northern Rockies and Plains 18.13 Ohio Valley 34.03 Northeast 19.36 South 39.07 Upper Midwest, Ohio Valley 18.42 Northeast 25.95 Northern Rockies and Plains 27.06 Upper Midwest 22.19 Upper Midwest 22.64 South 30.18 Upper Midwest 24.63 Northeast, Ohio Valley, Southeast 22.00 Northern Rockies and Plains 26.37 Northeast, Southeast 18.37 Southern and Eastern North America 19.62 Northern Rockies and Plains 21.99 Ohio Valley 20.14 Northeast https://www.climate.gov/news-features/featured-images/january-2016-snowstorm-was-category-5-event 26.97 Upper Midwest

Listed by month

MonthNumber of recorded stormsOctober1November3December2January8February6March3April3 Source National Climatic Data Center

See also

List of regional snowfall index category 4 winter storms List of Northeast snowfall impact scale winter storms List of blizzards

References