Turns out not just any jackass with a sprinkler in winter can make snow. The process is more complex than most people imagine, with variables such as wet-bulb temperature, humidity, droplet size, wind direction, nucleating agents, and...bacteria.
Back in the ’80s, scientists discovered Pseudomonas syringae, a bacterium first identified as a plant pathogen that grows on crops like wheat and corn. During cold spells, infected crops were much more susceptible to frost damage. Scientists realized the bacterium created a protein that allowed water to bind to the cell and freeze at higher temperatures than normal, which was obviously bad for crops—but potentially brilliant for snowmaking.
In order for water to freeze and precipitate as snow, it must come in contact with condensation nuclei in the air. In naturally occurring snow, the nuclei are typically dust particles, but the protein from the bacterium could also initiate this freezing process at much warmer temperatures.
So in 1987, a snowmaking additive named Snomax that uses the protein isolated from Pseudomonas syringae came on the market and was quickly adopted by resorts around the world. It hasn’t been without controversy—there has been no significant long-term research on its environmental effects—but most scientists (or at least the ones who ski in the East) agree the effects will likely be minimal.