Ski areas learned a long time ago that Mother Nature, on occasion, could use a helping hand ... so they came up with snowmaking.

Now, when there are no clouds and no snow in the forecast, resorts can simply turn on the guns and make snow. And they can therefore provide good skiing even in lean years.

It has, in fact, gotten so sophisticated that computers have now taken over a lot of the responsibility.

Deer Valley has computerized snow guns, programmed to sense ideal snowmaking conditions, and can begin spewing out the white flakes in the middle of the night and continued operating well into the morning hours, much to the delight of the staff.

With a simple click of a mouse, a computer operator can automatically call for snow when conditions are right — and walk away.

The computer then tells each snow gun when to turn on or off and which of 20-plus kinds of snow to make, from extremely dry to extremely wet.

Despite long periods between snow, with snowmaking and 7 inches of new snow that recently fell, bringing the season total to 6 feet, Snowbird opened two additional chairlifts over the weekend and now has 75 percent of its terrain open to the public.

Making snow dates back to the 1950s in New England. Ski areas found themselves slim on snow, so they decided to make it using garden hoses, sprinklers and compressed air. Soon, snowmaking companies started to spring up.

The air/water mixture is still used today, but on a larger scale. No more garden hoses and sprinklers. Among the new innovations is the snow fan. A large fan pushes water from nozzles out onto the slopes in the form of snow. The newest innovation is a snow gun that uses only water — no electricity or compressed air.

The amount of snow that can be made depends on a number of factors — temperature, relative humidity, wind, water temperature, volume of water, volume of compressed air and the size of the nozzle.

In Utah, historical temperature readings suggest there are about 200 hours of good snowmaking time in the weeks leading up to Thanksgiving and much more time in the weeks after.

Guns can start making flakes, on demand, when temperatures reach 28 degrees.

Deer Valley has about 150 snow guns spread over its slopes. Between 40 and 50 guns can be in operation at any one time. Once the snow has piled up, snowcats then move in to distribute it over the slopes.

Snowbasin has one of the world's most sophisticated snowmaking systems.