How Do Ski Resorts Make Snow?

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Ski resorts would love it if it snowed every day and only fresh, natural powder was used to groom the slopes for the entire season, but Mother Nature doesn’t like to be that cooperative. Instead, mountain resorts have to rely on artificial snow to coat the slopes throughout much of the ski season. However, the process of making snow isn’t as easy as it looks. Here’s how ski resorts make their own snow.

Natural Snow

Aerial view of mountain resort area with tram and distant, snowy mountain peaks in background
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In nature, snow comes from freezing water droplets in the atmosphere. As moisture forms inside of clouds, the droplets begin to freeze. The more they bump into each other, the larger the ice crystals get. Eventually, they become large enough to fall to the ground. If the ground temperature is cold enough, the droplets will remain frozen and accumulate. Just like the paper cutouts you made in elementary school, natural snowflakes are hexagonal. The intricate patterns are what help them to stick together when you’re making a snowman.

Early Snowmaking

Skiers and snowboarders in Vail resorts
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In the dry Connecticut winter of 1949, the owner of Mohawk Mountain Ski Resort, Walter Schoenknecht, refused to accept that there wouldn’t be snow on the mountain, so he ordered 700 tons of ice to be trucked in, crushed, and spread over one of the slopes. This probably didn't create the best skiing conditions, but at least it got people back on the slopes.

While trucking in ice might not have been the most efficient way of covering the slopes, it did spark an idea. In March of 1950, three amateur engineers who were inspired by Schoenknecht’s idea (Arthur Hunt, Wayne Pierce, and Dave Richey), designed the first artificial snowmaker.

They knew natural snow was made by freezing water droplets, so their idea was to shoot water droplets into the freezing air so that it would solidify and turn into snow. They took a spray-gun nozzle, hooked it up to an air compressor and a water hose, and built the very first D.I.Y. snow gun. They let the invention run overnight and came in the next day to find a 20-inch pile of snow covering a diameter of 20 feet. The project was a success!

Modern Snow Guns

Mountain snow groomer shoveling and preparing snowpack as a skiing surface
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Although they rely on the same basic idea of freezing water droplets in midair, modern snowmaking machines are much more complex than a spray-gun hooked to a garden hose. Today, ski resorts use two different types of machines to make snow:

  • Fan Snow Gun: This snowmaking machine looks like a giant hairdryer. Like its name suggests, this snow gun has a large, powerful fan in the middle with an array of tiny nozzles around the outer rim of the opening. There are two different types of nozzles: water nozzles that emit a fine mist and nucleator nozzles that use compressed air to split water droplets and form a small particle of ice. The ice particles from the nucleator nozzles are propelled into the air by the fan, where they fuse with the liquid water droplets to form snow.
  • Lance Snow Gun: These aren’t as powerful as their fan-driven counterparts, but are much cheaper and easier to maintain. Lance snow guns look like a really tall lawn sprinkler. They use compressed air to create a fine mist that comes out of the nozzles on top. The mist is allowed to freeze during the long fall to the ground.

It’s All About the Mix

Aerial view of skier preparing to slide down steep, snowy ski path on mountain slope
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Just because you have a big fancy snow gun doesn’t mean that you can simply turn it on and have snow. Ski resorts have a lot more to think about than just keeping the machines running.

Obviously, the first thing they need to consider is the weather. It’s pointless to use the energy and resources to make snow if it’s just going to melt in midair. The wet bulb temperature — the temperature that considers humidity and evaporative cooling — needs to be below freezing. Sometimes, the wet bulb temperature will be below freezing even when the dry bulb temperature (the one you see on the thermometer) isn’t.

Next, it’s important to use the coldest water possible to make snow. Many ski resorts have snowmaking ponds that collect rain and snowmelt throughout the season. These ponds are frequently at the top of the mountain to make sure they stay cold year-round. The water is carried up the hill using massive pumps.

Finally, it’s time to mix the air. Air that comes out of a compressor is hot and often over 180 degrees, which isn’t ideal for making snow. Before it can be sent to the snow guns, it has to be cooled to around 36 degrees Fahrenheit. Getting the air and water mixture just right to work with the natural conditions isn't an easy feat.

Natural Versus Artificial Snow

Chairlift over ski run with trees on both sides
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Many skiers claim that there’s no substitute for natural snow. The hexagonal shape of natural snow allows for a lot of air between flakes, which is what makes it so fluffy. Artificial snow is circular, which is why you won’t find powdery conditions on most maintained slopes.

While it’s impossible for snow machines to produce the “fluffiness” of natural snow, artificial snow is much tougher. After several runs, the arms of the natural snowflakes break off, which leads to deteriorating conditions. Since artificial snow doesn’t have any arms to begin with, it can withstand a lot more abuse.

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