A major snowstorm can happen during any month of the winter season, but in the northeastern United States, they tend to happen most often in February. In fact, February is the snowiest month of the year, on average, for most places across the region.
The reason for this has a lot to do with seasonal weather patterns. That is, certain weather patterns are more likely to develop at different times of the year in different places across the country. In February, that pattern is highly conducive to producing major snowstorms in the northeast.
In general, that set up involves a large ridge in the jetstream over the west coast of the US with a deep, negatively tilted trough, in the east. The trough allows cold air from the north to spill down over the region. This means that any precipitation that falls will likely come down as snow. Another key factor is the warm water of the Gulf Stream, which flows just off the east coast. Storms that pass over it tend to rapidly intensify. Then, following the jet stream northward, storms often encounter an area of high pressure over eastern Canada that slows their forward movement. As a result, more snow can fall over the same location boosting accumulation totals.
This is reflected in the statistics of the North East Snowfall Impact Scale (NESIS), which shows that the most category 3 or higher snowstorms occur in February. Ranked on a scale of 1 to 5, a category 3 is described as a “major” snowstorm, category 4 is considered “crippling”, and category 5 is an “extreme” event. The classifications are based on the size of the area covered, number of people affected, and snowfall totals.
In New York City, a winter season will produce 25.8 inches of snow, on average. Of that total, 9.2 inches comes in February.