How many inches of rain is equal to ten inches of snow?

Question

You always hear about the city that got 24 inches of snow in a day but never about an area that got that much so how many inches of rain is equal to 10 inches of snow?

Answer 1

The data is available if you know where to look. At most airports the NWS takes such data and lists it in their climate reports. Click on the map here for your region:

http://nws.noaa.gov

click on the local climate link on the left, and then the CF6 product for a location. There is also data from cooperative observers and some hobbyists & meteorologists - though that requires some searching.

As some others have stated, the snow:water ratio can vary - though none yet mentioned the great extent it can do so. Wet snows are sometimes 6:1, lake-effect snows 50:1 or more (though their snow amounts are often exaggerated and the ratio typically quite a bit less). There was one lake-effect snow of 2 feet just downwind from Lake Michigan when the air was calm - flakes gently piled up on top of another, and then a strong wind came and basically blew it all away!

I've taken quite detailed snow data here for the past 8 years:

http://www.joseph-bartlo.net/mtpdat.htm

and my ratio averages about the 10:1 people typically cite. Yet if you browse the data, you'll see the typical large (synoptic scale) storm goes from about 8:1 early & late in the season to about 13:1 midwinter. Cold air has something to do with that, but the most important thing is the temperatures in the "crystal factory" inside the clouds, because that determines the shape of them and how they stack when they fall:

http://www.teachervision.fen.com/weather/resource/3827.html
http://www.its.caltech.edu/~atomic/snowcrystals

Also mist can have an effect. ASOS sensors often detect "snow & mist" rather than just snow. If you look closely in such situations, you can see the mist droplets mixed in and this packs the snow down to some extent.

Snow showers tend to have high ratios - 20-30:1 not uncommon - such as February 1, 2000:

http://www.joseph-bartlo.net/feb2000.htm

That was about an hour & a half shower with a cold front. The one February 18 of that year was a synoptic storm system with warm flow aloft which changed to rain - the snow:water ratio being 8:1 before the changeover.

Answer 2

A rough rule of thumb is that one inch of rain is the same as ten inches of fresh snow but a lot depends on the type of snow that falls. Noticed that it's fresh snow, snow that's been lying for a while becomes compact so less depth equals an inch of rain.

The light fluffy snow contains much more air then the wet slushy stuff. One inch of rain could be the equivalent of as much as 20 inches of light snow (more in some circumstances) or as little as just a couple of inches of the heavy stuff.

Answer 3

It varies considerably with the moisture content of the snow, which depends on the temperature and humidity and other conditions. If the air is very cold and dry, the snow is light and fluffy, and it can take 12 inches to make 1 inch of water. If the temperature is near freezing, the snow can be very wet and heavy, and it may take only 6 inches to make an inch of water.

For a rough guess you could say that 10 inches of snow = 1 inch of rain, or a little more.

Answer 4

12 inches of snow equal 1 inch of rain

Answer 5

One inch or rain, will produce 10 inches of snow, if cold enough. The general rule of thumb, is for every inch of rain multiply by 10 and you will get an equivalent amount in snow.

Answer 6

Inches is a volume measurement. Liquids like rain are approximately incompressible so it is a pretty good approximation to consider the density of rain to be the density of water so reporting rainfall in inches makes sense, quantitatively. Snow obviously is compressible (snow balls snow men) so there is no good relationship between the volume of snow and its weight. (Same thing for the height of a column of snow). Height of a snowfall does give information about the potential travel difficulties , so it is not useless - just useful in a different way.
As the height of a snow column increases, it is compressed to a more predictable density and so we are able to quantify things like glaciers, icebergs and ice sheets.
There are rules of thumb out there that will give you some idea of the amount of air in a cubic inch of snow, depending on snowfall conditions. Happy hunting.

Answer 7

I think the comparison is that every 10" of snow is about 1" of rain.

Answer 8

There isn't a set rate for rain to snow.

Some snow is very wet & some is quite dry.

Only when you melt the snow would you know the ratio.

Answer 9

about 1 inch

I heard 1 foot (12 In) snow was equivalent to 1 in rain

Answer 10

probs about 5 times more....