The first, which is most common to the central United States, mirrors the way regular thunderstorms are formed: Warmer, moist air close to the ground rises and mixes with colder, denser air higher up in the atmosphere. As the hot air moves up and the cold air moves down, the atmospheric instability can trigger lightning and the thunder that comes with it.

In the case of a thundersnow event, air closer to the ground is just warm enough to rise and create atmospheric mixing, but it’s still cold enough that falling snow can stay frozen. This often happens in the Rockies, when the mountains trap pockets of warm air. “The air is cold enough down low that as the frozen precipitation falls out of it, it never encounters a warm enough layer of air to melt,” said Dr. Nielsen-Gammon. So instead of rain and lightning, there’s snow and lightning.

The second scenario tends to happen around the Great Lakes in early winter. A thunderstorm develops even though temperatures are very cold , thanks to the relatively warm moist air that comes from the lakes. It’s intertwined with the same conditions that bring the region its lake effect snow.

In the third scenario the low pressure of a powerful winter storm creates strong upward motions in the a ir, generating the atmospheric instability that in a typical thunderstorm would be driven by temperature changes. This is likely what led to New York City’s thundersnow.

Even when the conditions are right, you won’t always notice the thunder. Snow is more likely to absorb the light of lightning and the sound of thunder than rain.