It's one of the favorite questions any time we get rain in the winter: "How much snow would all this rain be?".
Let's start with the fun and generic answer. 10" of snow generally equals one inch of rainwater. Easy, right? Right. All you must do is melt snow to find the amount of water it holds. What’s not so easy is to do the reverse. You can’t freeze rainwater to make snow.
While rough estimates can be given there is no official conversion for rainfall to snow. That’s because of one big factor: Warmer air can hold more moisture than colder air. It’s why we have had 2, 3, even 4-inch rainstorms before but never 20, 30 or 40-inch snowstorms (if you tried to use the basic 10 to 1 conversion).
Each snowstorm has a different temperature structure in the atmosphere. Remember the weather surrounding us is three-dimensional and each storm is unique. At the start of this explanation we mentioned that generally 10” of snow equals 1-inch of rainwater. That is the average. Some snowstorms produce only 4” of snow for 1” of rainwater. That would be the heavy wet type of snow. Others produce 25” of snow for only 1” of rainwater. That is the powdery snow which is easy to blow around but doesn’t make for good packing.
Science has shown us that snowstorms are all unique and it’s fun to let our imaginations play. But how much snow would all that rain be? It’s probably a lot less than what you think, and we will never really know.