Dig in for the scoop on snow.
Snow comes in many sizes and an infinite number of shapes. This type of precipitation forms at all times of the year in clouds that are cold enough to allow their formation.
Snow forms when water vapor, the gas form of water, changes from gas directly to a solid, which are ice crystals, or snowflakes. This differs from freezing rain, which also starts as snow but melts to a liquid then freezes on contact with earth’s surface. Sleet also starts as snow but melts and then freezes into ice pellets before hitting the surface.
Snow crystals start out very small but can grow rapidly when there is a lot of moisture present. Snow will grow by taking more water vapor and adding ice crystals to what is already present.
Very large snowflakes occur when the outdoor temperature is at or slightly above freezing. As snow falls into the slightly above freezing temperatures, a thin film of liquid water forms on the snowflakes, which then allows colliding flakes to join together.
In very cold temperatures snow flakes are very small, because there is not a lot of moisture in the air to give them the opportunity to grow.
Is it ever too cold to snow? No! Think about the North and South poles. They are much colder than the Midwest, but it can still snow there. The snowflakes will just be very small.
Watch the Winter Precipitation video. Winter brings snow, sleet, freezing rain, and the dreaded polar vortex. Extension educator Duane Friend discusses the causes and differences between snow, sleet, and freezing rain, as well as other winter phenomenon, including Alberta Clippers, Pacific air, and the polar vortex. Understand trends in winter weather for the last 50 years and what we expected for the future, including winter weather preparedness.