The regional snowfall index (RSI) is a system used by NOAA to assess the societal impacts of winter storms in the United States. The scale is a replacement for the Northeast snowfall impact scale (NESIS) system, which was used for winter storms just in the Northeastern United States; Regional Snowfall Index assesses winter storm impacts in the six easternmost regions of the United States instead of just the Northeast. Since its initiation, the NCDC has assigned RSI values to nearly 600 winter storms since 1900.

Storms are ranked from category 0 "nuisance" to category 5 "extreme" on the scale. A category 4 winter storm on the RSI scale is classified as "crippling". 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. A category 4 "crippling" ranking is indicated by a numerical score between 10 and 18 on the scale.

Out of the nearly 600 historical winter storms assessed since 1900, only 74 storms have been given a category 4 or above ranking, 48 of which were category 4 storms. The highest ranking category 4 winter storm is the March 2–8, 1915 United States blizzard, which had an RSI of 17.67. The most recent storm to receive a category 4 ranking is the December 2022 North American winter storm, which scored an RSI value of 11.49. The following list orders the category 4 storms chronologically.

List of category 4 events This list includes all winter storms which had a maximum RSI value in the category 4 range. Storms that ranked as a category 4 in some regions but ranked as a category 5 in one or more other regions are not included in this list. Year Date Max. RSI Region 15.65 Northeast, South 10.16 Southeast 12.19 Northeast, South 11.34 Ohio Valley 16.09 Ohio Valley 17.67 Northern Rockies and Plains, South 10.61 South 10.62 Upper Midwest 13.97 Southeast 12.69 Northern Rockies and Plains 11.26 Southeast 10.18 Upper Midwest 10.63 Northeast 15.79 Northern Rockies and Plains 12.97 Upper Midwest 16.93 Northern Rockies and Plains 13.78 South 11.79 Southeast 12.66 Southeast 12.28 Northeast 10.14 Northeast 10.18 Northeast 12.52 Southeast 10.08 Upper Midwest 14.42 Ohio Valley 15.01 Southeast 10.81 Northern Rockies and Plains 10.55 South 15.14 Southeast 14.78 Southeast 15.18 Upper Midwest, Northern Rockies and Plains 13.16 Southeast 11.21 Ohio Valley 15.30 Upper Midwest, Ohio Valley 14.67 Northeast 11.31 Ohio Valley 10.34 Northeast 14.22 Northern Rockies and Plains 14.95 South 15.71 Southeast 10.15 Southeast 12.75 South 10.07 South 15.85 Northeast 11.80 South 10.66 Southeast 10.66 Northeast 15.7 Upper Midwest 15.826 Northern Rockies and Plains 11.49 Upper Midwest

Listed by month

MonthNumber of recorded stormsNovember2December7January7February17March10April4 Source National Climatic Data Center

See also

List of regional snowfall index category 5 winter storms List of Northeast snowfall impact scale winter storms List of blizzards

References