We are trudging through the cold into the next season of the year: Winter. The snow has started to fall, the ice has formed, and some people are still wearing shorts. How does snow form you ask? Perfect question! 

Well let’s start off with temperatures. In the US, we use the standard system of measurement, which isn’t very standard anymore. In Fahrenheit, the warmest temperature needed to produce snow is 32 degrees, or in Celsius, zero degrees. This is the freezing point for ice.

In these conditions, the normal water vapor will instantly form into ice crystals though ice doesn’t form unless there is pollution of some kind–not harmful gases or substances, more of grains of sand, soot, or ash. 

From there, the ice will continue to expand and grow heavier. This will lead to the falling of these crystals. I know everyone stays up at night just thinking, “Why is some snow more like a powder, and some really wet?” Well, finally, here is your answer. 

If the snow falls through warmer air underneath the cloud, it will either turn into sleet or rain. If it falls through moist air, the ice crystals will come out heavier than before, having collided with other ice crystals and bonding. If the crystals fall through cold air, they will become powdery and won’t stick together as easily. So if there is rain or sleet before a forecast of snow, there is a higher chance of having heavy packing snow. 

For snowballs, this is great. For the wheels of your car, not so much. Good luck throughout the rest of the winter everyone. May you all have good tire traction. And if you want to learn more about rain, sleet, or snow visit https://nsidc.org/cryosphere/snow/science/formation.html.