By Sam Collentine, Meteorologist Updated 7 months ago November 16, 2023

Snowmaking, Explained

snowmaking 101

Natural snow is the best kind of snow, but when it comes to preparing most ski resorts for the upcoming winter season, snowmaking plays a big role. Read on for our quick take on how snowmaking works.

Snow Guns

The function of a snow gun is to blow tiny water droplets into the air, let them freeze, and fall to the ground. There are two primary types of snow guns.

The first type of snow gun combines compressed air and water. The compressed air splits the water into tiny droplets, while also launching it high enough to allow for the droplets to freeze. 

The second type of snow gun combines a stream of water with an electric fan. Instead of compressed air, the electric fan blows the water into tiny droplets that freeze and fall to the ground.

Copper Mountain Snowmaking | October 3, 2019

Snow Forecast: Copper Mountain

Wet-Bulb Temperature

The best measure of snowmaking conditions is something called the wet-bulb temperature. This is the combination of the actual air temperature and the amount of moisture in the air. 

Normal Temperature + Humidity = Wet-Bulb Temperature

Snowmaking is most efficient when the wet-bulb temperature is well below freezing. However, snow can still be made when the temperature is near freezing as long as the air is very dry. 

Humidity (Key Ingredient)

Water droplets freeze more quickly when the air is dry, and this is due to an effect called evaporational cooling.

When the air is not saturated, some water droplets in the air evaporate from a liquid to a gas. This evaporative process requires heat, and this heat is taken from the surrounding air. Thus, the surrounding air loses heat and becomes cooler.

Think of when you step out of the shower with a few droplets of water on your skin, and you feel a slight chill as you enter a dry room. This is evaporational cooling.


32°F Temperature + 25% humidity = 24°F Wet-Bulb Temperature

This is well below freezing and plenty cold enough for efficient snowmaking.

Wet-Bulb Temp Guide for Snowmaking

Optimal: 10-20°F

Favorable: 8-10°F & 20-25°F

Marginal: 2-7°F & 25-28°F

Unfavorable: <2°F & >28°F

Below is an internal, experimental OpenSnow forecast for the wet-bulb temperature.

The purple and blue dots indicate favorable snowmaking conditions, while the orange and red dots indicate less favorable snowmaking conditions.

Bill LeClair Q&A | Snowmaking Manager at Arapahoe Basin

snowmaking explained

When does snowmaking typically begin at Arapahoe Basin?

A-Basin typically starts making snow sometime between late September and early October. It’s entirely dependent on conditions, but it’s also good to get open. A-Basin has only been making snow since the 2002-2003 season.

What snowmaking advantages does A-Basin have over other ski resorts?

Simply put, the elevation is A-Basin’s advantage. (Base = 10,800’; mid-mountain = 11,500’, top of lift-served terrain = 12,500’). We get the right temperatures and that helps us make better-quality snow. Once we get going, there’s nothing to stop us. We have a small system compared to others but we just crush it. It’s a team effort from the snowmakers, the groomers, the ski patrol, and mountain ops; everyone has a role to play.

What are the biggest constraints for snowmaking at A-Basin and in general?

The biggest constraint is water. A ski area can only take so much. That said, only about 10 percent of the water we use is lost to evaporation. Most of the water A-Basin uses for snowmaking ends up right back in the source. Another minor constraint is that A-Basin starts making snow on the intermediate High Noon run. Steeper slopes require more snow for coverage, and High Noon is a little on the steep side (relatively speaking). But it’s also shorter, so it takes less snow to cover from top to bottom.

What does a typical shift look like for the snowmaking team?

The A-Basin snowmaking team will work 10-hour shifts in the early season, then rotate 12-hour shifts to keep snowmaking happening 24-7. The snowmakers are constantly monitoring the conditions and communicating with one another. It takes about 45 minutes to fire up the system, from getting the water pumps going to fill the lines, to physically walking among the snow guns to get each one turned on and warmed up.

snowmaking wet bulb temperature

The magic number for A-Basin is a 26°F wet bulb temperature. Warmer than a 26°F wet blub temperature and I think the snow quality is not good. As temperatures drop, we can use more water. The goal is to get something between wet and dry snow. If you can make a snowball and squeeze water out of it, that’s too wet. If you can see rainbows in the plume of the snow gun, that’s too wet. The large piles of snow are called “whales” and once they’re big enough, we like to let them “cure” for 24 hours to let the water leech out. That leaves better-quality snow for the cat drivers to push.

Anything else that you would like to add?

A-Basin's snowmaking consists of a fleet of 24 energy-efficient fan guns plus an arsenal of low-energy stick guns. The whole thing is solar-powered thanks to our partnership with Xcel Energy and its Renewable Connect program, giving us access to a large-scale solar project in eastern Colorado.

The snowmaking team starts on High Noon, then works its way out and up the mountain, covering Sundance, Ramrod, Wrangler, Molly Hogan (the learning hill), and then up to the top following Dercum’s Gulch and Lenawee Face. When A-Basin first opens, guests are able to take one lift ride and then ski or board back to the base, with no downloading required.

snowmaking arapahoe basin

Snowmaking is critical far beyond just being able to open early. Quality snowmaking is also really important to setting a good base for the entire season.

Thank you so much, Bill!

Snow Forecast: Arapahoe Basin

Download the OpenSnow app and stay tuned to our forecasts for the latest weather updates. 

Sam Collentine

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About The Author

Sam Collentine


Sam Collentine is the Chief Operating Officer of OpenSnow and lives in Basalt, Colorado. Before joining OpenSnow, he studied Atmospheric Science at the University of Colorado, spent time at Channel 7 News in Denver, and at the National Weather Service in Boulder.

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