Measuring Snow

  • Installation

    The 4" diameter rain gauges that we use for NeRAIN can be used for measuring the water content of snow. However, you must remove the inner measuring cylinder and funnel for measurements of snow water content and other freezing/frozen precipitation. The inner tube can easily crack and break if moisture collects and then freezes. But keep the funnel and measurement tube handy indoors -- you'll need it.


    Have a ruler or yardstick ready(ideally one that measures in inches and tenths). You should have a snow board (a flat board, painted white, ideally about 16" x 16"). They come in very handy for measuring snowfall. You will need to identify a good representative location that is as flat and level as possible where snow accumulates uniformly and does not melt prematurely. Wooden decks are OK, but they should be at least 20-30 feet away from your house since your house will affect snow accumulation patterns. You may need to have warm water handy(tap water will be fine).


  • Measuring precipitation - The water content of snow

    The snow (rain, freezing rain, etc.) will collect in the 4" diameter outer cylinder (overflow cylinder). If snow collects on the rim of the gauge you have to decide what belongs in or out of the gauge. Just take a book or flat object and push gently straight down on the top of the gauge. Whatever falls in is in, and whatever falls out is out. It may not be perfect, but at least it's objective. With wet snows, a lot of snow can collect on the rim, so it makes a difference.

    Bring the gauge inside at your time of observation. If it has stopped snowing, you can bring it in earlier and just let the snow melt. But you may need to hasten the process. In order to measure the water content of snow with this type of gauge, you will need to melt the contents and pour them back into the calibrated inner cylinder.

    You may take your inner calibrated cylinder and pour warm water into it and jot down the amount. Then add that warm water to the outer cylinder so that all the snow melts. Then pour the water back into the inner tube and record the total amount. For example, lets say you added 0.51" of warm water to the snow. Then when you measured the total sample, it read 0.82" How much precipitation did you get? The answer should be 0.31"

    0.82" - Total of melted snow with the added warm water
    -0.51" - Total warm water added to melt snow
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    0.31" - Daily Precipitation (the amount you should report)

    Make sure you avoid spilling. It can happen.

    During heavy snow (6" or greater) the cylinder will fill to the top and overflow with snow. You will have to measure more often than once daily under heavy snow conditions.

  • Measuring snowfall - New snow amount

    Snowfall is the maximum accumulation of fresh snow during the past day prior to melting or settling. We measure snowfall to the nearest 0.1 (one-tenth) inch. Since snow melts and settles, you may have to measure during or soon after snow ends in order to capture how much accumulated. By 7 AM the next morning there may be less.

    For example if the snow begins to fall in mid morning, accumulates to 4.2" by 3 PM and then stops and begins melting and settling such that by 7 AM the next morning you only have 2.6" of snow on your snowboard, then the correct number to report for your 24-hour snowfall (new snow amount) is 4.2" -- the accumulation prior to melting and settling. If the ground was bare prior to this snow your snow depth (total depth of snow on the ground) would be rounded to the nearest half inch and would be reported as 2.5 inches.

    The trick in measuring snow consistently is simply finding a good place to measure and a firm surface (such as a snow board) for your ruler to set on. Some people use low picnic tables, some use their car. I don't recommend sidewalks since they tend to accelerate melting. Grass is where snow accumulates first, and it is OK to measure on grassy surfaces, but please know that the snow tends to sit up on top of the blades of grass, sometimes by one to three inches. Your ruler, on the other hand, will go right down through the snow and grass to the ground and give you an exaggerated reading. Just be careful to measure to the bottom of the snow not to the ground.

    Measuring new snow accumulation is easy when the snow falls without wind and isn't melting on the ground. But when the wind blows, measuring snow becomes a real challenge. We deal with drifted snow by simply taking many measurements from a variety of locations and averaging them to get a representative measure. You will get the hang of this -- with experience.

    If you use a snowboard, take a core sample and then be sure to clear the board after your measurement and set it in a nearby location level on the surface of the new snow. If you leave it down in a depression, it will tend to collect more snow from drifting if the snow continues to fall.

  • Snow depth - Total depth of snow on the ground

    Snow depth is simply the total depth of snow on the ground at your scheduled observation time (hopefully 7 AM or close). Snow depth is measured to the nearest half inch. It includes both new and old snow, and should be reported even on days when no new snow has fallen. If necessary, take an average of several measurements. For example, if half the ground has 2" of old snow and the other half of the ground is already bare, the average snow depth would be 1".

  • Snow cores - Core precipitation

    Under some circumstances (primarily strong winds), your 4" diameter gauge will not catch all of the snow that has fallen. You can watch windblown snow crystals curve around a rain gauge like water going around a rock in a river. If you believe your gauge has not adequately caught the precipitation that has fallen (or, if you're just curious), then take a core sample of the fresh snow that has fallen. After first measuring the water content in the gauge, take the 4" outer cylinder and "cut a biscuit" in the fresh snow by pushing it straight down. It is best to do this on your snowboard (after you've measured the snow depth, but before you have cleared the snow and put it back on the surface). Use a thin sturdy cookie sheet or something similar to slide under the cylinder so that you can lift it up without spilling the contents. Be sure to measure in a representative location -- not in a drift or in a wind-blown or melted area. Then proceed to melt and measure the water content like you would with any other measurement.

  • Snow book

    "The Snow Booklet": A Guide to the Science, Climatology and Measurement of Snow in the U.S" can be ordered from the Colorado Climate Center. You can also download by clicking the link: A Guide to the Science, Climatology, and Measurement of Snow in the United States