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The Science behind Snow

-Houston, TX
 snow snowflake snowfall winter updraft humidity wind temperature cold science environment weather crystals

Snow is a key sign of winter time. Many people enjoy the beautiful scenery and fun activities associated with it on a yearly basis. Despite its regularity in some areas, the process of snow falling is often magical and mysterious. Looking at the scientific process behind the formation of snow can help to clear up this mystery.

The PROPER Conditions for Snow

Before snow can form, the atmosphere needs the right weather conditions. The temperature needs to be below freezing (0 degrees Celsius or 32 degrees Fahrenheit) and there needs to be sufficient moisture in the air. Moisture ensures that there are water particles in the air that can turn into snow, and the low temperature ensures that the particles freeze rather than falling as rain. There is no limit for how low the temperature can be, but lower temperatures often reduce the humidity as well, making it more difficult for snow to form. Once the temperature reaches about -10 degrees Fahrenheit or -20 degrees Celsius, there is usually insufficient humidity for snow to form. The last condition needed for snow to form is updraft, or warm air particles moving upward as cool air particles move downward. Updraft works against gravity and supports particles as they form in the atmosphere. The more updraft there is, the more it will be able to support larger particles and the heavier the snow will be.

How Do Snowflakes Form?
 snow snowflake snowfall winter updraft humidity wind temperature cold science environment weather crystals

Once all of the right conditions are met, snowflakes can begin to form. Snowflakes occur when water droplets freeze on dust particles in the atmosphere creating an ice crystal. As these crystals begin to fall to the ground, water vapor builds new crystals off of the primary crystal making six symmetrical snowflake arms. The branching often seen in snowflakes is due to changes in atmosphere as the snowflakes fall, changing the path of crystal formation. Each snowflake has a unique pattern because each snowflake has a slightly different path as it falls to the ground.

When Snow Reaches the Ground

The differing effects of humidity, temperature, and wind on snowflakes becomes even more apparent as snowfall reaches the ground. The higher the water-to-snow ratio of the snowflakes, the denser the snow becomes. This means that more humid areas often have heavy snow which clings to surfaces and is more difficult to shovel. Temperature also affects the texture of snowfall, as snowflakes can melt on their way to the ground or on hot surfaces. This gives snow a slushy or watery consistency. Wind can also affect the texture of snow as it falls. Strong wind breaks up snowflakes into smaller crystals, giving the snowfall a more granular texture

Snow is one of the best parts about the winter season, and learning the complicated process in forming snow makes it seem even more magical. Stay curious and cozy this winter!

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