We’re nearing the month of February, and that is when the Northeast United States typically experiences their worst snowstorms. These snowstorms are measured by the NESIS, or Northeast Snowfall Impact Scale. This scale, developed in 2004 by Paul Kocin and Louis Uccellini of the National Weather Service, categorizes the winter storms that affect the Northeast. There are five categories: Extreme, Crippling, Major, Significant, and Notable. These rankings from the NESIS scale are based on a calculation that factors in the area affected by the snowstorm, the amount of snow, and the number of people living in the path of the storm. With this calculation, it then leads to the NESIS number. If the number is greater than or equal to one, then it makes the scale. Also, the higher the number, the higher the category and therefore more impactful the storm is.
So far, 59 winter storms have made the NESIS and only two have earned the distinction of category 5, or Extreme. This includes the snowstorm of 1993 in March and a Blizzard of 1996. The storm in 1993 is holds the highest NESIS number at 13.20.
Now based on these 59 storms that are ranked by the NESIS, the majority have occurred during the first half of February. Therefore, on average, the most impactful storms that hit the Northeast happen during the month of February.