The past weekend’s blizzard may be somewhere out over the Atlantic now, but it’s left its last official mark in the record books here in the U.S. On Tuesday, scientists at the National Centers for Environmental Information (NCEI) released their analysis for the storm, showing that it ranked among the top 10 most severe winter storms to hit the Northeast and Mid-Atlantic in more than 100 years.

NCEI uses a measurement known as the Regional Snowfall Index to rank the severity of winter storms. The scale is similar to the Saffir-Simpson scale used to rank hurricanes but also takes into account how many people were affected by a storm in addition to how prodigious the snowfall amounts were.

Nearly 103 million people — roughly a third of the entire U.S. population — dealt with impacts from the storm including flooding, heavy snow, ice and wind. In all, 21 million people had to contend with at least 20 inches of snow from the storm.

Blizzard 2016 RSI rank

A snowfall map and RSI score for this weekend's bizzard.

That’s enough for this storm to rank as a Category 4 winter storm, which NCEI describes as crippling. Based on the score that goes with the rank, this storm will go down as the sixth-most severe winter storm on record for the Northeast. NCEI’s records include 199 winter storms to hit the region since 1900. It ranked as the fifteenth-worst storm on record for the Southeast out of 153 winter storms recorded since 1900.

This storm had the smallest geographical footprint among the top 10 strongest winter storms to hit the Northeast, but the area it hit the hardest also happened to be one of the most densely populated swaths of land in the country.

While the Category 4 ranking illustrates how severe the storm was, it doesn’t take into account one of the most lasting impacts of the storm: coastal flooding and beach erosion. The storm took a huge bite out the Jersey Shore and Delaware coastlines, leaving those areas vulnerable to future storm surge when the next storm hits.

Because of all these impacts, the storm is expected to be a multi-billion-dollar disaster.