The Science of Snowflakes

Close up of a snowflake
soul-images / Getty Images

After learning these big facts about these little crystals, you may never look at a snowflake the same way again.  

1. Snowflakes are not frozen raindrops.

Snowflakes are an aggregation, or cluster, of hundreds of ice crystals that fall from a cloud. Frozen raindrops are actually called sleet. 

2. the Tiniest Snowflakes Are Called "Diamond Dust."

The smallest snow crystals are no larger in size than the diameter of a human hair.

Because they're so small and lightweight, they remain suspended in the air and appear like sparkling dust in the sunlight, which is where they get their name. Diamond dust is most often seen in bitterly cold weather when air temperatures dip below 0° F.

3. Snowflake Size and Shape Is Determined by Cloud Temperature and Humidity.

The reason why snow crystals grow this way is still somewhat of a complicated mystery... but the colder the air surrounding a growing snow crystal is, the more intricate the snowflake will be. More elaborate snowflakes also grow when the humidity is high. If temperatures within the cloud are warmer, or if humidity within the cloud is low, expect the snowflake to be shaped like a simple, smooth hexagonal prism.

If Cloud Temperatures Are...Snowflake Shape Will be...
32° to 25° FThin hexagonal plates and stars
25° to 21° FNeedle-like
21° to 14° FHollow columns
14° to 10° FSector plates
10° to 3° FStar-shaped "dendrites"
-10° to -30° FPlates, columns

4. According to Guinness World Records, the Largest Aggregate Snowflake Ever Reported Fell in Fort Keogh, Montana in January of 1887 and Allegedly Measured 15 Inches (381 Mm) Wide!

Even for an aggregate (clump of individual snow crystals), this must have been a monster snowflake! Some of the largest non-aggregate (single snow crystal) snowflakes ever observed measure 3 or 4 inches from tip to tip.

On average, snowflakes range in size from the width of a human hair to less than that of a penny.

5. the Average Snowflake Falls at a Speed of 1 to 6 Feet per Second.

Snowflakes' light weight and fairly large surface area (which acts as a parachute slowing their fall) are the primary factors affecting their slow descent through the sky. (In comparison, the average raindrop falls roughly 32 feet per second!). Add to this that snowflakes are often caught in updrafts that slow, halt, or even temporarily lift them back up to higher altitudes and it's easy to see why they fall at such a creeping pace.

6. All Snowflakes Have Six-Sides, or "arms."

Snowflakes have a six-sided structure because ice does. When water freezes into individual ice crystals, its molecules stack together to form a hexagonal lattice. As the ice crystal grows, water can freeze onto its six corners multiple times, causing the snowflake to develop a unique, yet still six-sided shape. 

7. Snowflake Designs Are a Favorite Among Mathematicians Because of Their Perfectly Symmetrical Shapes.

In theory, every snowflake nature creates has six, identically shaped arms. This is a result of each of its sides being subjected to the same atmospheric conditions, simultaneously.

However, if you've ever looked at an actual snowflake you know it often appears broken, fragmented, or as a clump of many snow crystals — all battle scars from colliding with or sticking to neighboring crystals during its trek to the ground. 

8. No Two Snowflakes Are Exactly Alike.

Since every snowflake takes a slightly different path from the sky to the ground, it encounters slightly different atmospheric conditions along the way and will have a slightly different growth rate and shape as a result. Because of this, it is highly unlikely that any two snowflakes will ever be identical. Even when snowflakes are considered to be "identical twin" snowflakes (which has occurred both in natural snowstorms and in the lab where conditions can be carefully controlled), they may look strikingly similar in size and shape to the naked eye, but under more intense examination, small variations become evident.

9. Although Snow Appears White, Snowflakes Are Actually Clear.

Individual snowflakes actually do appear clear when viewed up close (under a microscope). However, when piled together, snow appears white because light is reflected by multiple ice crystal surfaces and is scattered back out equally into all of its spectral colors. Since white light is made up of all the colors in the visible spectrum, our eyes see the snowflakes as white

10. Snow Is an Excellent Noise-Reducer.

Have you ever gone outside during a fresh snowfall and noticed how silent and still the air is? Snowflakes are responsible for this. As they accumulate on the ground, air becomes trapped between the individual snow crystals, which reduces vibration. It is thought that snow cover of less than 1 inch (25 mm) is enough to dampen the acoustics across a landscape. As snow ages, however, it becomes hardened and compacted and loses its ability to absorb sounds.

11. Snowflakes Covered in Ice Are Called "Rime" Snowflakes.

Snowflakes are made when water vapor freezes onto ice crystal inside of a cloud, but because they grow inside of clouds that also house water droplets whose temperatures are cooled below freezing, the snowflakes sometimes collide with these droplets. If these supercooled droplets of water collect and freeze onto nearby snow crystals, a rimed snowflake is born. Snow crystals can be rime free, have a few rime droplets, or be completely covered with rime. If rimed snowflakes blob together, snow pellets known as graupel then forms.

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