Technology of Snowmaking

Snowmaking basics

How is Snow Made?
When nature doesn’t cooperate by providing natural snow, snowmakers take over. Given water, electric or diesel energy, and temperatures below 32°F (0°C) snowmakers can provide snow.
Basically, snow is small particles of ice. So, the really old way of making snow, and the way they still do in the tropics and for special events, is to grind up blocks of ice. However, this is very expensive and labor intensive for larger scale requirements, so, if possible, machines that convert water into snow directly and on site are used.
These snowmaking machines make snow by breaking water into small particles, cooling the water by causing them to move through cold air, nucleating the water particles and distributing the resulting snow on a surface. Why don’t people just sprinkle water to make snow? Water is a unique material, it expands when it freezes and it has high heat of fusion, thus your ice cubes float and last a long time. Heat of fusion means that one can cool a pound of water say from 65°F (18.3°C) to 64°F (17.8°C) or 34°F (1.1°C) to 33°F (.6°C) by removing 1 BTU. But to convert one pound of liquid water at 32°F (0°C) from a liquid to one pound of ice at 32°F (0°C) requires the removal of 144 BTUs. In summary, a large amount of heat removal (cooling) is required in snowmaking. Also, water can be cooled well below 32°F (0°C) and still stay a liquid unless it is nucleated. This phenomenon is called supercooling.
So a snowmaking machine (a) breaks the water into small particles, (b) cools the water to 32°F (0°C), (c) removes the heat of fusion, and (d) nucleates. Snowmaking requires relatively large quantities of water, for example, to cover an area of 200 feet (61 meters) by 200 feet (61 meters) with 6 inches (15 centimeters) of snow, one would need 20,000 cubic feet (566 cubic meters) of snow. This would require 10,000 cubic feet (283 cubic meters) or 74,600 gallons (282,392 liters) of water. Thus, an excellent water supply is needed and the water pressure should be at least 100 PSI (pounds per square inch) (7 Bar) or 230 feet TDH (total dynamic head).
Many ski areas can convert over 5,000 gallons (18,900 liters) per minute of water into snow. This is 20 tons per minute or 1,250 tons per hour. Snowmaking, while usually used at ski areas, is also used for frost protection on construction projects, freeze protection of crops, automotive and aircraft testing, and sewage disposal. There are over thirty snowmaking companies around the world. SMI® is one of the largest companies dedicated primarily to snowmaking.
Miscellaneous Snow Facts
Quiet snow. Ever wonder why a fresh snowfall seems so peaceful? One reason is that freshly fallen snow muffles sound. Air pockets get trapped between flakes as they land, and the air pockets help absorb sound.
Snowflakes. Snowflakes form in much the same way raindrops form. Water vapor freezes onto microscopic bits of dust, salt or other nuclei creating tiny ice crystals. Winds throw the crystals up and down in the clouds, causing them to merge with others or grow with the help of super cooled water droplets.
Cold snow. Not all cold places have lots of snow. Air that is too cold contains little or no moisture and snowflakes cannot form. Snowflakes are much more common in the northern United States than at the North Pole!
Blizzards. A blizzard is the most dangerous type of snowfall. Winds must be at 35 miles per hour (56 kph) at temperatures below 20°F (-7°C). These conditions cause the snow to whip around and significantly lower visibility.
Barometric pressure. Due to gravity, our atmosphere has weight. About a ton of air is pressing down on you all the time, but you don’t feel it. That’s because the same air pressure surrounds and supports you. Air pressure is measured with a barometer. When air is cold and dry, it weighs more (high pressure), so the barometer is higher in fair weather. When air is wet, it actually weighs less (low pressure), so the barometer is lower when it is raining. Changing barometric readings indicate a change in weather. A falling barometer indicates a change in weather. A falling barometer indicates precipitation is rising. A rising barometer means clear skies are on the way. In snowmaking, generally a clear cold night creates the best conditions for optimal production on high pressure nights.
Dew point. The temperature air would have to be cooled in order for saturation to occur. The dew point temperature assumes there is no change in air pressure or moisture content of the air.
Wet bulb temperature. The lowest temperature that can be obtained by evaporating water into the air at constant pressure. The name comes from the technique of putting a wet cloth over the bulb of a mercury thermometer and then blowing air over the cloth until the water evaporates. Since evaporation takes up heat, the thermometer will cool to a lower temperature than a thermometer with dry bulb at the same place and time. Wet bulb temperatures can be used along with the dry bulb temperature to calculate dew point or relative humidity.
Machine-Made vs Artificial Snow
Our industry prefers to use the term “machine made snow” when describing the snow produced as it is actual snow. We do not like to use the term “artificial snow” as it is not fake or imitation snow. The product produced uses mainly water and some compressed air to help freeze water droplets into snow. Machine made snow typically has no dendrite arms due to the short hang time and is more like small aggregate material.
What is Curing?
Snow is typically produced in piles and stored in piles to allow the water droplets time to thoroughly freeze. Some snow is only frozen like an egg shell and it takes time to freeze 100% the total droplet. So most resorts prefer to leave snow in piles for 8 to 10 hours before pushing them out.
However, snow can also be produced that is very dry and totally frozen within seconds of leaving the snowgun. So snow can be made that is skied on during production.
Snow Gun Types
There are generally two primary snowmaking snowgun technologies commercially purchased today – fan and stick/lance. The concept of using nucleation to help freeze the majority water spray still applies to both technologies.
Fan snowguns use propeller driven ducted fans to help throw the snow and provide hang time for mixing and freezing. Fans are known for long snow projection and throw, high capacity in all weather conditions, low wind sensitivity and overall performance. Fans can be portable or fixed position on towers and swing arms. Stick/lance snowguns are generally tower mounted with either 6 meter or 9 meter mast heights. This extra height allows some hang time via gravity. These snowguns have limited throw and are very sensitive to the wind.
Snow gun types
There are generally two primary snowmaking snowgun technologies commercially purchased today – fan and stick/lance. The concept of using nucleation to help freeze the majority water spray still applies to both technologies.
Fan snowguns use propeller driven ducted fans to help throw the snow and provide hang time for mixing and freezing. Fans are known for long snow projection and throw, high capacity in all weather conditions, low wind sensitivity and overall performance. Fans can be portable or fixed position on towers and swing arms. Stick/lance snowguns are generally tower mounted with either 6 meter or 9 meter mast heights. This extra height allows some hang time via gravity. These snowguns have limited throw and are very sensitive to the wind.
Why Select a Fan or Stick?
Both technologies are popular today. The fans are more popular in area with marginal weather conditions and wider slopes. The sticks are more common in colder climates with narrow slopes. Both types are offered with manual and automatic control options.
What is SmartSnow™?
SmartSnow is a software and controls package that operates and acts as the brain for a snowmaking system. Input variables like weather, water temperature, snow quality, water pressure help determine the snowgun adjustment to achieve the desired snow quality selected. The entire system can be operated via computer, tablet or smartphone.
SmartSnow has been in development for over 20 years and provides excellent energy and resource management along with provided resorts with comparative data.
Why Does Snowmaking Use Wet Bulb Temperature?
Wet bulb condition factors on both ambient temperature and relative humidity to help define the coldest condition a water droplet can obtain. It is related to the temperature reading on a thermometer when its mercury bulb is moistened. This reading is typically colder than the actual dry temperature. So humidity plays a great role in droplet freezing along with the temperature. The colder and drier the conditions, the more effective snowmaking becomes.
Download a PDF of our Wet Bulb Charts

Advanced Snowmaking

Weather Volatility

Whether or not you believe in global warming and climate change, here are some facts to consider:

  • 19 of the 20 hottest years have occurred since 1980
  • Worldwide temperatures have warmed one degree Celsius over the 20th century
  • More than 20% of the Polar Ice Cap has melted in the past 30 years
  • Climate change can result in more air pollution and problems with water supplies as precipitation patterns change. The effects are much greater at extreme latitudes on both ends of the earth and at higher elevations.

We don’t know with certainty what the future will bring, but that doesn’t mean you do nothing. Just the opposite. Develop a well-thought-out and logical plan for your resort.

Intelligent snowmaking investments will continue to help stabilize your mountain resort business. Adapting strategies and practices in anticipation of less natural snow, and less snowmaking time under the condition of higher snowmaking temperatures coming in smaller windows, will force your team to improve. The goal is to improve your energy intensity or the energy used per cubic foot of product produced.

As the famous scientist Pascal claimed, “…given the possible outcomes, the upside of being prepared and ready for a fearsome event surely beats the alternative.”

Weather volatility is here and is not going away, and our ability to forecast the weather remains difficult for more than about seven days out. Your continuing investment in snowmaking and working with companies like SMI that have experienced, talented people and products can only help improve your chances for success.

Improving the Future of Snowmaking

So, what can you do to improve snowmaking? Consider the following:

  • Secure water rights now
  • Add water supply and storage now
  • Invest in new snowgun technologies that are much more energy efficient
  • Add fans to wide trails to get 100% width, even in “bad years”
  • Invest in automation for your plant
  • Invest in automation for snow guns and maybe hydrants as an option
  • Buy a good, reliable, fast-acting weather system like SMI’s SmartSnow using aspirated weather stations
  • Our industry theme for snowmaking should follow NSAA’s policy to reduce, educate and advocate for change
  • Promote the fact that snowmaking returns over 80% of the water used. We are not consumptive. Stored water as snow during the winter saves it for future use in the spring
  • New snowmaking technologies have better water-to-snow conversion rates and are much more effective energy users
  • Snowmaking allows health and fitness benefits to millions in winter who go outside and enjoy
What is Snow Quality?
In general, snow quality is defined by snow density or percentage water content. Density is mass per volume in kg/m³ or #/ ft³. Water content is measured per snow depth or volume of melt water within a given volume. Here are some density examples:
Material KG/M3
Sea Water 1030
Fresh Water 1000
Ice 920
Snow 50-600
Air 1.3
Ice floats on water due to being lower density. In snowmaking, we often think of snow quality in terms of the classic snowball test of squeezing water out, or the sleeve test on a cold jacket – does it splat or bounce? You Have Snow Quality Options. In SMI’s automation programs we use 10 snow quality setting options with one being the driest setting. Wet bulb, water temperature, water pressure and water flows are all considered in the settings. Here is a density summary table with 5 general setting examples for water content relative to snow quality your resort might use.
Quality Water Content Description
5 50% Wet slushy snow
4 42-50% Base snow, wet in marginal
3 35-42% Good skiable snow
2 25-35% Light and dry, snowballs flake off
1 25% Very dry, can’t make a snowball
Snow Quality Affects Volume

Snow quality definitely impacts snow volume, while nucleation and water droplet mixing, hang time and cure time also affect the snowmaking process. As you know, there is a big difference in cost and productivity at 29°F (-1.5°C) and 0°F (-18°C). We suggest you discuss snow quality on a regular basis throughout the time of snow production. Understand the costs and capabilities within your snowmaking system and snow gun fleet for making dry snow or base snow at different wet bulb conditions.

More Water Does Not Always Equal More Volume

One of the areas that we all need to be reminded about is that more water through a snow gun does not directly result in more snow on the ground. Over the past few winters SMI has been testing new nucleation technologies and nozzle types and positions. We have tested in conditions between 29°F (-1.5°C) and -2°F (-19°C) with water temperatures of 34-35°F (2°C) and frozen water content between 24% and 55%. More than 100 tests have been completed.

Snow Gun Choices

Traditional Air/Water

  • Uses more than 200 cfm (5.67 cmm) of compressed air per snowgun
  • Internal mix nucleation
  • Typical short tower or sled mount
  • High energy and noise
  • Good in marginal conditions with decent snow throw


  • Simple nozzle PoleCats and Pumas to multi-nozzle Wizzards
  • Various carriage and tower mounts
  • Excellent overall snow production
  • Excellent throw
  • Good energy usage and low noise levels

Low and Moderate Energy Towers

  • Uses less than 180 cfm (5.0 cmm) of compressed air per snowgun
  • Typical 6m to 9m tower mount or 3m to 5m sled mount
  • Internal or external mix nucleation
  • Good energy usage
  • Possible limited marginal and cold condition production
  • Possible limited throw
  • SMI’s V2 at 20 cfm to 180 cfm Fans

Water Sticks

  • Water only towers that use additives for nucleation
  • Decreased popularity due to limited marginal temperature production
  • Limited throw
  • Added cost a factor
Snow Gun Selection Factors

Selection Factors

  • Snow production in various temperatures and humidity levels
  • Throw
  • Sensitivity to winds
  • Ease of operation
  • Noise
  • Appearance – are towers acceptable
  • Tower heights
  • Tower positions – trail edge or middle
  • Water pressure requirement
  • Cost Considerations
  • Initial capital cost for equipment and system
  • Energy costs
  • Labor costs
  • Maintenance costs
  • Additive costs
  • Transport costs
  • Grooming costs to push snow out from piles

In addition, we encourage resorts to consider snowgun performance and snow quality under multiple conditions such as: in mild years, typical years, cold years, and under good wind and bad wind conditions.

  • What type of spacing of snow guns is required to connect the piles?
  • What types of throws versus trail widths are needed?

As you can see, there are many factors that go into the snow gun selection process. We want you to educate yourself on as many parts of snowmaking as you can to help make a better-informed decision.

Understanding Snow Gun Flow rates

Understand existing snowgun flow rates at 28°F, 24°F and 20°F wet bulb, and do not just believe the manufacturers. Go out and measure water and air flows with flowmeters. And check snow quality and snow density. What happens if conditions move up or down 2°F?

Mounts for snow guns matter. Generally, the taller the tower, the better the production – up to about 40 feet in height. Any taller and the support mechanisms become quite significant. Wind impact is also a big consideration above 40 feet.

Air flow rates have a direct cost correlation to energy costs so define air volume closely.

What is the range of performance for your snowgun fleet?

  • On/off snow guns
  • One valve and flow steps
  • Multiple valves and flow step
  • Infinite adjust of air and water
  • What happens to snow quality?
  • How does your on/off work when it is marginal or cold?
    Sweet spot is likely about 4°F of range!

These are some areas for your team to focus on as the snow guns utilized remain the biggest predictor for costs.

Smarter Snow and Cost Reduction

As you evaluate snowmaking at your resort, focus on the variables you can control.

1. Where to Start? Define your operating costs:

  • Energy, labor, maintenance, depreciation, additive and transportation
  • What is your grooming cost to push out the piles?
  • Historical water volumes
  • Historical hours of operation
  • Historical average temperatures and humidities by month
  • Inventory water and air systems
  • Inventory hydrants and snow guns
  • Inventory snow gun types and mounts

2. Work Through Start Up Scenarios:

  • Who is defining the opening strategy?
  • Trails, depth, full width?
  • Are you making snow on the right trails guest desire?
  • Or is your focus the easy to make snow on trails?
  • Do you have the correct snow guns on trails?
  • Are you using lowE on 250’ wide trails?
  • How long does it take to change trails and startup snow guns?
  • How much water can you convert to snow at 28°F wet bulb, 25°F wet bulb?

3. Evaluate Existing Snow Gun Fleet:

  • What are the water and air flows consumed at three different temperatures? (see “Understanding Snow Gun Flow Rates” in previous section)

4. Evaluate Snow gun Options. (See “Snow Gun Choices” in previous section)

5. Fixed Position Versus Portable. Moving from portable snow guns to fixed position snow guns can result in huge savings on primary trails. When you consider set up time, burying snow guns, digging out snow guns and the time to take down and put away or park, these costs and difficult work environment are a real challenge. The labor and lost snowmaking time generally justify a fixed snow gun on primary trails.

Now it certainly depends on winds, trail, priority, existing infrastructure, snow volume per snow gun and other factors to help determine if fixed position snow guns will be effective. SMI has many manual customers that can start 150 fan snow guns in less than an hour with five snowmakers. The key is they are towers with the cords, hoses and orientation ready to go. Add automation and they can be started even faster.

Some larger resorts with ground air guns on sleds or tripods may make three ribbons on a 200’ wide trail. In other words, they set up on the far 1/3 of the trail and make snow, then move all 50 guns over 60 feet to hit the middle third and so on. Why not just add tower fans that throw the entire width?

6. Grooming Costs. Are you using lowE towers or small throw air snow guns with little throw on 200’+ wide trails? So the snow is basically positioned in a big butterfly pile 20’ to 70’ from the snow gun. So grooming times are huge to push it across the trail to get to full width. So instead of 30 hours cat time to open, it may take 90 hours. At $100/ hour that is $6,000. Using oscillating tower fans will cut time down dramatically.

7. Automation Levels. The majority of snowmaking snowgun automation is with fixed position snow guns. Consider the height of the tower and the convenience of access for service and maintenance. Automation factors to consider are many and include starting, adjusting and stopping/draining. Is the start full open or throttling with pressure control? Does the adjustment involve valves and pressure control? Does the snow gun shutdown and drain on fault or power loss? Is there intelligence at the snow gun? Can it run without communications or a link to the master computer? What is the flow range of the snow gun at your resort? What type of communications are used? Hardwire, fiber optic and radio modems are commonly used today in snowmaking.