There’s Actually a Difference Between “Snowfall” and “Snow Depth”

Snow days no doubt bring joy to children as they anxiously watch the news to see if the weather might cause a school day cancellation. There are actually two measurements you might hear on those reports: snowfall and snow depth. Snowfall is the amount of snow that falls in a single storm or in a certain time period. Suppose you want to calculate how much snow fell during a single night. Because the grass and air at the bottom of the ground can interfere with your measurement, the National Weather Service recommends using a snowboard (or any 16x16-inch piece of plywood) because it provides a hard, flat wooden surface. You just need to find a spot that’s easy for you to walk to and gives you a 45-degree angle of the sky all around you. Then, place something tall you can see, like a flag, on top of your snowboard so you can see it after the snow falls. When you wake up the next day, take a ruler to measure the amount of snow on the snowboard. If the height of the snow varies, take at least 3 measurements to get the average measurement. 


Snow depth is something entirely different. It’s the total amount of snow currently on the ground. Most of the time, the amount of snowfall and the snow depth are likely to be the same during a storm. However, there are times when these measurements can vary. According to NWS guidelines for snow measurement, if snow changes to rain or sleet, those interested in an accurate snowfall measurement need to do so before the weather changes. Rain can condense or melt the snow already on the ground, making the snow depth measurement different from how much snow actually fell. For example, if the snowfall amount was 4 inches before turning into rain, it would alter the amount of snow on the ground, making the snow depth 3 inches when the rain ends. Which measurement means your kids are getting a snow day? Knowing what amount of snowfall or snow depth will trigger a school closing is tricky and hard to predict. At the end of the day, it’s not the amount of snowfall or snow depth that will cancel school — it’s how prepared your community is to weather the storm.