Each year in wintertime, we see snow spreading over our gardens, our streets, our fields and yet, we don’t always know how it forms, what it is made of, or what its benefits are.

What is snow made of?

Snow is made of snowflakes mainly composed of crystalline water ice coming from tiny supercooled cloud droplets. This homogeneous mix of cloud droplets only occurs at temperatures lowers than -35°C. A snowflake consists of approximately 1019  water molecules added at different rates and in different patterns.  Snowflakes are also made of dust and polluted air.

When does it form?

Snow forms when the tiny super cooled cloud droplets freeze. These tiny crystals stick together in clouds to become snowflakes. If enough ice crystals stick together, they will become heavy enough to fall to the ground. Snowfall occurs when the air temperature is below 2°C. If the temperatures get warmer then it will melt and fall as rain.

What are the benefits of Snow for the earth?

You may not know this but snow has many uses in the natural world. A major benefit of a thick snow cover is that it will function as an excellent insulator for the soil. In wintertime, if there were no snow, the ground would freeze deeper and deeper, leading to damage to the root system of trees and shrubs. It also helps conserve soil moisture over the winter and is often a very useful source of water especially in hot, dry countries. Rivers like the Nile or the Indus in India would dry up in hot weather without supplies of melting snow. Snow also enhances the visibility of some landscape plantings, such as red twig dogwood or river birches, making them greener.