Ski resorts make snow to start the ski season earlier and end it later, and to fill in when Mother Nature doesn't supply enough of the white stuff. Learning how to make snow is part science and part art. The men and women who make snow have learned how to transform water into the right size water crystals with the right consistency to create a light, flully base for skiing and snowboarding.
Snowmaking starts with the right equipment. The resort needs miles of piping to pump water to the slopes, as well as big compressors to manufacture compressed air and blowers to spread the snow around. Nature has to cooperate as well, with a water source for the thousands of gallons of water needed to make enough snow to cover slopes, and temperatures below freezing to make and hold the snow.
Before ski slopes open for the season, crews work through the night making snow to cover at least a few ski runs. Snow-making crews are often specialists contracted by the resorts to work all or part of a season. Top crews work year-round, traveling to North America in October and working their way to South America and Australia as the North American resorts shut down for summer.
Snow-making occurs at night because temperatures are cooler then. They need consistent temperatures in the 20s to make snow. In addition, the best snow forms when the humidity is low, so resorts keep a close eye on both temperature and humidity in order to determine the best conditions for cranking up the snow guns. When it's time to make snow, crews pump water into a snow gun, which shoots the water out with compressed air. The combination of air and water creates tiny ice crystals which freeze as the fall, making snow.
The snow is usually blown into towering piles, which are spread over the slope with snow-grooming machinery. The result is a white carpet skiers can glide down. With luck, Mother Nature will add the real thing to this man-made base. Snowmaking allows resorts to open to the public earlier in the year and to offer good skiing regardless of the weather. Those early openings come at a high price however. The New York Times reported in 2001 the cost of snowmaking equipment was $40,000 an acre to install and an additional $1,700 an hour to operate — not counting the labor to pay the crews to run the machinery.
Still, few major resorts in the United States operate without at least some snow-making. Man-made snow tends to be icier and pack harder than the real thing, and some powder snobs disdain skiing on man-made snow. But when December rolls around and the skies have been stingy, most skiers are happy resorts have learned how to make snow.