8 inches of snow =how many inches of rain/water?

Just wondering how many inches of snow equal how many inches of rain/water? Is there an easy formula for this?

“I think it speaks to the duality of man sir.”
(private Joker in Full Metal Jacket)

The answers are:
It depends

We get an average of 60 or 70 inches a year here and the water content varies a great deal. It must depend on the upper level conditions where the snow is formed.
I think they actually take a measured volume of snow and either weigh it or melt it to get the water content.

I’d always heard that it was a ten-to-one ratio on average (IE, ten inches of snow being an equivalent to one inch of rain). That “on average” disclaimer is important. though, as there’s a lot more water content in a heavy snow than in a light, fluffy one.

No, there’s no easy formula. It varies widely. Back when I was in high school (1967)the stock answer was 20:1. That is, twenty inches of snow would melt to one inch of water. That was blindly accepted for years. Now we know that wind-driven, drifted snow, for example, is denser than fluffy snow. A hundred other variables make it impossible to answer the question without melting the stuff down. How do we know that the stock answer was only sometimes true? Somebody tested the accepted standard, instead of accepting it. There’s a lesson in that for all of us.


The practical conversion that applies in most cases (and that meteorologists use to determine snow predictions) is 1 inch of rain = 10 inches of snow.

However - and I just found this out from my dad - while this is a good rule of thumb, it is NOT always the case. He told me that the weathermen where he is (DC) said that one reasoon that this storm confounded them as to it’s snow amounts was because it was closer to 1 inch of rain = 20 inches of snow!

I do not know how this varies or why.

Yer pal,

Cecil’s take:

  • Rick

PS - Note the critical difference between Northern and Southern hemispheres for this subject! :slight_smile:

Damn simulposts…

One of the most important measurements of snowpack content occurs in the Sierra Nevada every late winter. The snowpack of the mountains is measured for its water content. The method is actually simple; they weigh the snow taken by a standard core sampler. This tells them how much water is frozen in the snow.

I can’t recall this for sure, someone can check, but IIRC the people who do all this measurement work for the various Northern California area utilites districts with dams that generate power in the lower Western Sierra.

Well, as taught to us at the University of Southern Indiana, in a Meteorology class (I earned an A), like has been stated before, the general rule is TEN inches of snow generally equals ONE inch of rain. Of course, if it’s an extremely dry snow, that ratio will be higher…possibly approaching 20:1 as in what happened in Raleigh, or lessening, to an extent.

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