"Earthbound snow guns, however, don’t always have the benefit of the atmosphere’s cold temperatures. Thus, artificial snowmakers have borrowed some nucleation ideas from on high to help water freeze more rapidly at temperatures closer to –5 °C or higher.
One such product is Snomax, a freeze-dried protein powder sold by Snomax International in Denver that gets mixed into the water pumped uphill to snow guns. Snomax derives its nucleating ability from Pseudomonas syringae, a bacterium commonly found on agricultural crops and other plants, as well as in the atmosphere. P. syringae has a powerful nucleating protein on its cell surface, with which it creates an icy spear to pierce plant cells and then feast upon their contents.
Drift, a snowmaking additive launched in 2001 by Aquatrols in Paulsboro, N.J., is a liquid polyether-substituted trisiloxane that acts as a surfactant. By reducing the surface tension of the water sprayed out of snow guns, this surfactant helps the droplets freeze more rapidly rather than clump together, says Andy Moore, the sales director for Drift. This ability helps increase the high-temperature window for snowmaking by about 1 °C and can improve snow quality at lower temperatures . . "
https://cen.acs.org/articles/96/i6/What-s-artificial-snow-and-how-is-it-made.html
http://www.dailymail.co.uk/news/article-3360831/Could-Swiss-skiing-holiday-make-ILL-Snomax-fake-snow-banned-Austria-Germany-used-Alps-bad-health-says-French-study.html
Very COLD WEATHER . . . http://www.bbc.com/sport/winter-olympics/42885124