Most of Earth’s inhabitants have never seen snow. For them, its sudden appearance becomes a grand event
Snow is a special type of precipitation that falls as ice crystals. It forms when air temperatures are below freezing and there’s sufficient humidity. When water vapor freezes, tiny crystals form and gather into snowflakes. They settle on the ground if the temperature remains low enough to prevent melting. Every year, a septillion snowflakes fall on Earth: 1024, or 1,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000.
In cold regions of our planet, such as Siberia or Greenland, snow falls and remains for many months. However, most of Earth’s inhabitants have never seen snow. For them, its sudden appearance becomes a grand event.
Snowflakes form from tiny droplets that attract dust particles and freeze. Interestingly, the initial size of snowflakes is microscopic—no more than 0.1 millimeters in diameter—but as they descend, they accumulate new crystals from moisture droplets in the air. Thus, not only snowdrifts but also snowflakes themselves can “grow.”
The weight of individual snowflakes is negligible, but together they’re much heavier than they appear. For example, if snow covers an area of 1 hectare with a 1-centimeter layer, it would equate to about 30 cubic meters of water. That’s roughly a month’s worth of water usage for a family of six, including bathing, dishwashing, cleaning, and cooking—or a full 28-meter pool or 2.5 months of active watering for a 600-square-meter garden.
What Snow is Made Of
Pure snow can be completely transparent, but snowflakes often capture other tiny particles in atmospheric layers
At the core of every snowflake are water molecules arranged in a complex crystalline lattice. However, snowflakes are only about 5% water—the rest is air. Pure snow can be completely transparent, but snowflakes often capture other microscopic particles in atmospheric layers. These mainly include:
Dust, including cosmic and volcanic dust, and mineral particles—these affect snow’s color, especially near the sea or in industrial regions where snow may appear slightly gray or brown.
Microorganisms—found in snowy areas of the globe. Some algae, for instance, can turn snow red. This phenomenon is called “watermelon snow.”
Types of Snow
Snow may seem like an ordinary phenomenon, but its diversity is truly astounding. The type of snow depends on external factors: temperature, atmospheric humidity, wind, altitude above sea level, and microscopic particles around which crystals form. Different types of snow occur in specific regions and climates, and understanding their properties helps us comprehend atmospheric processes. There are distinct types, categories, and configurations of snowflakes.
Dry Snow
Dry snow consists of light, fluffy crystals that scatter easily upon impact. It forms at low temperatures (usually below -10°C) and low humidity. Dry snow particles have sharp edges because they freeze almost instantly without time to dissolve or compact.
This type of snow is common in northern regions of Russia, such as Yakutia. In these areas, winter temperatures remain stable, and the air is dry. In Yakutia, for example, winter lasts up to 7 months a year, with average temperatures reaching -30°C—ideal conditions for dry snow.
Wet Snow
Wet snow is heavy and sticky, easily compacting
Wet snow is heavy and sticky, compacting easily. It falls at temperatures around 0°C when snow crystals begin to partially melt but remain frozen. Wet snow is perfect for making snowballs and snow sculptures.
Wet snow is typical in temperate latitudes. In Japan, especially on Hokkaido Island, wet snow creates famous snow accumulations in mountainous areas.
Fluffy Snow (Powder Snow)
Fluffy snow forms in light frost (between -5°C and -10°C) with high humidity. Its crystals are large, resembling “stars,” and accumulate easily, creating a soft, almost airy layer.
Powder snow can be found in Washington, Alaska, and mountainous regions of Switzerland, France, and Italy. In central Russia, fluffy snow often falls at the beginning of winter when temperatures aren’t too low.
Snow Grains
Snow grains are small, round crystals that form when snowflakes partially melt in warm, moist air layers and then refreeze in colder layers. This structure makes them particularly light and brittle.
Snow grains fall at around -5°C and are more common in mountainous or coastal areas where warm and cold air alternate. They’re typical on the west coasts of Canada and the U.S., in cities like Vancouver or Seattle.
Snowflakes
Snowflakes are large, fluffy crystals consisting mainly of star-shaped patterns and can reach several centimeters in diameter. They often occur in low wind and moderate humidity. During thaws or heavy snowfall, they can grow exceptionally large.
Snow Crust
Snow crust is a dense layer formed after partial melting and refreezing of the snow surface. It’s common in northern countries like Sweden and Finland
Snow crust forms when the snow surface partially melts and then refreezes. It typically appears after a thaw when sunlight warms the top layer, followed by a temperature drop that freezes it into a crust.
Snow crust is rare in forests and fields of central Ukraine but frequent in northern countries like Sweden and Finland. In Siberia, it’s observed in spring when sunlight intensifies. In the Alps, it increases avalanche risks. In cities, it’s hazardous for walking as it can conceal slippery ice underneath.
Firn
Firn is old snow that has undergone multiple freeze-thaw cycles. It’s denser than fresh snow but less dense than ice. Firn is common in high-altitude regions and glaciers where snow never fully melts.
Firn snow is typical in Antarctic and Greenland glaciers, as well as the Alps and Himalayas. In the Swiss Alps, old snow forms multi-layered “blankets” that eventually turn into dense glacial ice.
Glacial Snow
Glacial snow is multi-year compacted snow that transforms into ice under pressure. It has a dense, uniform structure, making it more resistant to melting.
Such snow covers can be found in Antarctica, Alaska, and high mountains like the Himalayas and Andes. In Antarctica, ice can move several kilometers annually, with glacial snow slowly shifting toward the ocean to form icebergs.
Pack Ice
Pack ice is multi-layered polar snow compressed into massive ice blocks over three meters thick, having undergone at least two summer melting cycles.
Though mostly found along coastlines, pack ice is nearly completely desalinated. It has a distinct blue hue.
Pack ice is primarily seen in Arctic zones and seas like the Chukchi, Greenland, and East Siberian Seas, as well as channels of the Canadian Arctic Archipelago. Some ice floes are so large that drifting research stations are established on them.
Diamond Dust
Diamond dust consists of tiny, glittering crystals that form in extremely low temperatures and high atmospheric pressure. It often falls in clear, frosty weather when moisture gradually crystallizes from the air.
Diamond dust can be observed in extreme cold, such as Antarctica or northern Canada and Siberia. In Yakutia, it’s especially vivid during winter nights below -40°C when the air is saturated with tiny ice crystals shimmering in moonlight or streetlights.
Watermelon Snow
Such snow covers can be found in Antarctica, Alaska, and high mountains like the Himalayas and Andes
Watermelon snow is a unique phenomenon occurring on high-altitude peaks in spring and summer when snow partially melts from within. From a distance, mountains appear to “bleed.” Aristotle first mentioned bloody snow, and the first samples were taken in Greenland in 1818 during Captain John Ross’s expedition. Initially, it was thought that rock and soil particles colored the snow.
Scottish botanist Robert Brown proposed another theory—algae particles in the atmosphere that fell as snow. A century later, this was confirmed under a microscope. The red pigment was named “snow chlamydomonas.” Watermelon snow is named not only for its color but also for its distinctive aroma released by sun-activated algae. It’s most commonly seen on Sierra Nevada slopes.
Unique Snow Conditions Around the World
Russia: In northern regions like Yakutia and Siberia, winter lasts over six months with heavy snowfall. Snow persists even in late May. In Yakutsk, diamond dust can be observed below -40°C.
Japan: Hokkaido Island and Niigata Prefecture receive vast amounts of wet snow due to a unique combination of maritime climate and mountain ranges. Japanese “snow walls” can reach 20 meters high.
Saudi Arabia: In some desert regions, like the north, snowfall is possible in winter. In 2021, snow caused a sensation among locals.
Antarctica: Despite its location, little snow falls due to low humidity, but any snow that does fall rarely melts and gradually compacts into glaciers.
How Snow Forms
The transformation of water vapor into snow crystals occurs through several stages:
Evaporation and ascent—moisture evaporates and rises until it reaches cold atmospheric layers.
Condensation—as it cools, water vapor condenses into tiny droplets and freezes.
Crystallization—ice crystals form and combine into snowflakes. Snowflakes fall to the ground when they become too heavy to stay airborne.
Main Snowflake Shapes and Formation Conditions
Largest snowflakes and records: Snowflakes average 1 to 5 millimeters in diameter. However, under certain conditions, much larger crystals can form. Record-breaking snowflakes were recorded in Montana in 1887—some reached 38 cm in diameter!
Needles
Needles are long, thin crystals that form around -2°C. At this temperature, crystals grow elongated, resembling miniature icicles. Such snowflakes often fall as light snow or crystals that quickly compact.
Flat Six-Pointed Stars
Flat stars form between -12°C and -16°C. These are among the most symmetrical and well-known snowflake shapes, with six branched arms. Water vapor freezes rapidly on crystal edges, creating intricate patterns. These are the classic “snowflakes” depicted in illustrations.
Dendritic Crystals
At -12°C and high humidity, dendritic snowflakes with long, branching structures form. These are some of the largest snowflakes, reaching nearly a centimeter in diameter. Higher humidity increases branching as water molecules freeze faster.
Columns
Columns or hexagonal prisms appear around -5°C. These are short, thick crystals where water molecules freeze into six-sided shapes without expanding laterally like stellar snowflakes. They create dense, smooth snow cover.
Plates and Thin Discs
Flat plates form between -10°C and -20°C with low humidity. Unlike stars, they’re simpler—thin and nearly smooth. They create a dense layer when falling. In low humidity, they have minimal branching, appearing as flat hexagons.
Sectors and Columns
Columns are hollow or solid hexagonal structures forming between -3°C and -5°C. Their inner parts don’t crystallize, while outer edges harden.
Factors Affecting Snowflake Shape
Overall, snowflakes depend on atmospheric phenomena, primarily temperature and humidity, which determine their shape and size. Each crystal is unique, and their structure can vary significantly based on conditions.
Temperature
The primary factor influencing snowflake shape and size is formation temperature. As temperature fluctuates, water molecules freeze at different rates, creating varied crystalline structures. For example, at -2°C, needle-like crystals form, while at -15°C, intricate six-pointed stars emerge.
Air Humidity
High humidity promotes complex, branched structures like dendrites. In drier conditions, simpler forms like hexagonal plates occur. More water vapor leads to denser snowflake structures as additional molecules create intricate patterns.
Air Pressure and Lift
Pressure and upward air motion affect snowflake shape and size. Faster air currents cause water molecules to combine more quickly, forming denser crystals. For instance, intense updrafts during snowstorms produce larger, more complex snowflakes.
Formation Altitude
At high altitudes with low temperature and humidity, snowflakes become simple hexagonal plates. At lower altitudes with higher temperatures, complex forms like dendrites or large stars are possible.
Crystallization Rate
Slow crystallization allows for more intricate shapes as crystals have more time to grow. Rapid cooling results in simpler, symmetrical structures.
Why Snow is Important
If snow hadn’t cooled Earth millions of years ago, life might not have been possible
Snow’s importance among precipitation types is vastly underrated. It played a crucial role in our planet’s biological development. If snow hadn’t cooled Earth during the “Snowball Earth” period 720-635 million years ago, life might not have emerged. After warming, cyanobacteria flourished, leading to the Cambrian explosion. Without ice ages, Earth might have remained a lifeless hot planet like Venus.
Snow continues to play vital roles in ecosystems and climate:
Moisture source—melting snow feeds soil with water in spring.
Insulation—protects plant roots and soil from freezing.
Temperature regulator—snow reflects sunlight, preventing overheating.
Habitat—provides shelter for insects and small animals during winter.
Snow Types by Precipitation Mechanism
Snow also varies by how it falls:
Continuous Snow
Continuous snow falls during prolonged cold cycles, typically as a soft, even layer without strong winds. It’s common in regions with persistent, heavy snowfall under stable temperature conditions.
Characteristics:
falls evenly and gradually
can accumulate thick layers
occurs under weak atmospheric fronts without sharp temperature or pressure changes
In Sweden, continuous snowfalls often occur in Jämtland and Västerbotten, starting lightly and lasting up to three days at around -5°C, forming dense but not wet snow cover.
Heavy Snowfall
Heavy snowfall is intense and brief, accompanied by strong winds and blizzards. It can create rapid accumulations, disrupting transportation.
Heavy snowfalls are common in Japanese mountains and northern U.S. regions, where winter storms dump massive snow amounts within hours.
Snow Grains
Snow grains are tiny flakes that melt quickly while falling, resembling drizzling rain. They occur near 0°C or during transitions between rain and snow.
Characteristics:
falls as fine flakes or granules
doesn’t accumulate significantly
occurs in humid weather near freezing
Snow grains are typical in coastal temperate regions like western Europe or the Black Sea area, where temperatures rarely drop below 0°C.
Why Snow is White
At high concentrations, light undergoes multiple refractions within snow crystals, reflecting rather than absorbing. This is perceived as white by human vision
Snow’s whiteness comes from light refraction and reflection within ice crystals. Air gaps between crystals cause light to scatter repeatedly. While individual crystals are transparent, collectively they appear white.
Physicist Kenneth Libbrecht explained this spectral phenomenon: at high snowflake concentrations, light refracts multiple times off crystals, reflecting rather than absorbing. This is perceived as white by human vision—similar to polar bear fur.
Massive ice blocks appear bluish because blue light reflects more strongly in the spectrum. Here we explain why icebergs aren’t just white.
Can You Eat Snow?
Snow near populated or industrial areas may contain pollutants—dust, soot, exhaust fumes, heavy metals, and other harmful substances absorbed by snowflakes.
Theoretically, snow is edible but not always safe. Snow is frozen water and, if uncontaminated, can be consumed. However, snow near populated or industrial areas may contain pollutants—dust, soot, exhaust fumes, heavy metals, and other harmful substances absorbed by snowflakes.
Eating snow makes sense only in pristine environments like high-altitude regions or Antarctica, where snow is clean enough for water. However, it should be melted first, as solid snow doesn’t provide sufficient hydration.
