geologyMcAfee SECURE sites help keep you safe from identity theft, credit card fraud, spyware, spam, viruses and online scams

Home » Water » How Do Snowflakes Form?

How Do Snowflakes Form?

The life of a snowflake begins high in Earth's atmosphere and if the snowflake is very lucky it might reach the ground.

A Tiny Particle High in Earth's Atmosphere

A snowflake begins when a tiny dust or pollen particle comes into contact with water vapor high in Earth's atmosphere. The water vapor coats the tiny particle and freezes into a tiny crystal of ice. This tiny crystal will be the "seed" from which a snowflake will grow.

Hexagonal Crystals

The molecules of water that form each tiny ice crystal naturally arrange themselves into a hexagonal (six sided) structure. The result will be a snowflake with six sides or six arms.

The image of a snowflake at right has six arms. These six arms reflect the hexagonal structure. Ice crystals are "minerals" because they have this natural hexagonal crystalline structure.

The Snowflake Grows as it Falls

The newly-formed ice crystal (snowflake) is heavier than the surrounding air and it begins falling. As it falls towards Earth through humid air more water vapor freezes onto the surface of the tiny crystal. This freezing process is very systematic. The water molecules of the vapor arrange themselves so that the hexagonal crystal structure of ice is repeated.

The snowflake grows larger and larger as it falls, enlarging the hexagonal pattern.

Every Snowflake is Different!

Although all snowflakes have a hexagonal shape other details of their geometry can vary. These variations are produced by different temperature and humidity conditions of the air through which the snowflake falls. Some temperature/humidity combinations produce flakes with long needle-like arms. Other conditions produce flakes with wide flat arms. Other conditions produce thin, branching arms.

These different shapes have an unlimited number of variations, each representing the conditions of temperature and humidity and water vapor encounters that the snowflake experiences during its fall. A collection of snowflakes is shown at right. Notice how very different they can be.

snowflakes - unique shapes
Photographs of many snowflakes showing how each has a hexagonal crystalline structure but a unique geometry. The shapes of the flakes are determined by the atmospheric conditions experienced as it fell through the sky. Conditions of temperature and humidity can change as the flake falls and cause variations in crystal growth. Image by NOAA. Click image to enlarge.

Will They Reach the Ground as Snow?

Mount Rainier Volcanic Hazards
What is a Debris Flow?
Types of Volcanic Eruptions
Mineral Rights
The formation of snowflakes high in Earth's atmosphere does not guarantee snowfall on Earth's surface. That will only happen if air temperatures are below freezing all the way to the ground as shown in the cartoon at right.


If the snowflakes pass through a thin warm layer of air they could experience partial melting. When they exit the warm air they will refreeze on the way down in the form of a tiny ice pellet. This is how sleet forms. For an illustration see the cartoon at right.

Freezing Rain

If the snowflakes pass through a layer of warm air that is thick enough to melt them completely, then land on a cold Earth surface, the result could be freezing rain. For an illustration see the cartoon at right.

The Complex Work of Meteorologists

Meteorologists have a challenging job. If they forecast snow they need to determine when a moisture laden air mass will pass over an area, they also need to determine if the temperature high at the snowflake forming elevation will be below freezing, and determine if the temperatures will allow the snowflake to fall to the ground, and finally know the conditions on the ground to determine if the snow will accumulate or melt.

If you think this is interesting and like to be challenged then you might make a great meteorologist.   :)


The Only Diamond Mine in the USA
What is Geology?
Diamonds Don't Form From Coal
Types of Volcanic Eruptions
San Andreas Fault
Blood Diamonds
Rare Earth Elements

snowflake - hexagonal crystal structure
Photograph of a snowflake that reveals the hexagonal (six-sided) crystalline structure of ice. This crystalline structure makes ice a "mineral". Image by NOAA.

atmospheric conditions for snow
Snowflakes form high in the atmosphere. They will reach the ground if air temperatures are below freezing all the way down. Image by NOAA.

atmospheric conditions for sleet
Snowflakes form high in the atmosphere. If they partially melt on the way down then refreeze before landing the result will be sleet. Image by NOAA.

atmospheric conditions for freezing rain
Snowflakes form high in the atmosphere. If they melt completely on the way down then land on a cold Earth the result will be freezing rain. Image by NOAA.

Find it on

More from

Impact Events
Impact Events: Articles and images about impact events on Earth, moons and planets.
Fluorescent Minerals
Fluorescent Minerals glow with spectacular colors under ultraviolet light.
Plate Tectonics
Plate Tectonics: Articles and maps about plate tectonics and the interior of Earth.
Cave of the Hands
Cave of the Hands: A cave in Argentina with wall paintings that date back to about 7000 BC.
US Gemstones
United States Gemstones: A diversity of gemstones are produced in the United States.
Plate Tectoncs
Zoom in on Plate Boundaries: See the details of plate tectonics in satellite view.
Pictures of Opal: A collection of different types of opal from all around the world and Mars too!
Sliding Rocks
Sliding Rocks Mystery: What causes these rocks to slide across a Death Valley playa?

Minerals in the News
$20,000 for a Canary Diamond Found in Arkansas:  Tana Clymer, a 14-year-old from Oklahoma City found...

Lateritic Rare Earth Deposits:  The Arizona Geological Survey has published Chapter 4...

Rock and Mineral Identification:  The ability to identify rocks and minerals in...

Military Armor Inspired by Twinning in Mollusk Shells?:  “The shells of a sea creature, the mollusk...

Mineral Hardness Picks:  Mineral hardness picks are pencil-like tools that have...

History of the San Manuel-Kalamazoo Mine:  The Arizona Geological Survey has published “History of...

geology news
Daily news delivered to you free by RSS or email.
Go to Geology News! Receive Daily News by Email Subscribe to Geology News Feed

© 2005-2014 All Rights Reserved.
Images, code and content of this website are property of Use without permission is prohibited. Pages on this site are protected by Copyscape.