10 Fascinating Facts You Might Not Know About Snow

Although snow and ice can be a nuisance on roads and sidewalks, it’s undeniably magical to wake up to a thick layer of snow blanketing the landscape. Many of us dream of a white Christmas in particular, but even after the festive holiday has passed, a heavy snowfall can lead to the joy of a snow day off from school or work. People who are used to dealing with flurries each winter might think that they already know everything about snow. Still, some of the facts on this list are as surprising as they are fascinating.

Related: 10 Inventive Ways People Survived Winter Before Electricity

10 Naturally Made Snowballs Sometimes Wash Up on Beaches

In 2016, thousands of snowballs as large as 3 feet (about 1 meter) across were found piled up along an 11-mile (17.7-km) stretch of beach on the Gulf of Ob, in northern Siberia. But although the snowballs looked as though they were shaped by human hands, they were actually made by waves.

The snowballs start as irregularly shaped pieces of sea ice that become rounder as they’re jostled by waves. They can grow when seawater freezes onto their surfaces, which also helps to make them smoother. The snowballs sometimes wash up on shore thanks to the wind or tide.

Siberia isn’t the only place where this cold-weather peculiarity has been found. In 2019, thousands of snowballs—some as small as eggs and some as big as footballs—were found along the coast of Finland’s Hailuoto Island. Massive snowballs also washed up along Lake Michigan’s shoreline in the winter of 2015, although they weren’t quite as smooth.^[1]

9 Igloos Can Be 70°F Warmer Than Outside

Sitting in a building made of snow to warm up in freezing temperatures may seem counterintuitive, but igloos can be up to 70°F (21.1°C) warmer than the air outside. This is largely thanks to snow being composed of around 95% trapped air. Because the heat in the air cannot easily escape, snow is a great insulator. Although ice might seem like a more stable building material than snow, it’s not nearly as warming due to being solid and largely airless.

Trapped air isn’t the only reason why igloos are so warm. Their structural design also plays an important role. Traditionally, igloos have different levels rather than a flat floor. Cold air sinks into a carved-out well at the bottom, while warmer air stays on the upper level where people tend to sleep.^[2]

8 Snow Monsters Grow on Mount Zaō

Mount Zaō in northern Japan is famous for the strange snowy formations that adorn its slopes. The figures are called “juhyo,” or “snow monsters,” and it’s not hard to see why, with the snowy shapes resembling mystical winter creatures.

The snow monsters are actually fir trees covered in snow and ice. Weather conditions need to be just right for the strange shapes to form: winds must blow consistently at about 85 feet per second, and temperatures must remain between 21°F and 31°F. These strong winds are laden with supercooled water droplets, which freeze when they come into contact with the branches of the evergreens. As the layers of ice build, they curl over into strange shapes.

Recent snow monsters have been smaller than those in previous decades. This is a major concern for businesses on and around Mount Zaō because the snowy trees are a massive draw for tourists. Not only is global warming leading to less-than-ideal conditions for ice to form, but moth and beetle infestations have also left the trees with fewer branches for ice to cling to.^[3]

7 Thundersnow Is a Rare Winter Weather Phenomenon

Thundersnow is essentially a thunderstorm in which snow falls instead of rain. It’s a fairly rare phenomenon—so rare that for many years, scientists struggled to secure funding to study it because some people didn’t believe it was real. Thundersnow is harder to notice than a typical thunderstorm because lightning is more difficult to see against a white sky, and snow absorbs sound waves, meaning thunder doesn’t travel as far.

Over time, evidence for thundersnow has accumulated, and scientists now have better technology to study the phenomenon. Thundersnow forms under similar conditions to a regular thunderstorm, involving turbulence in the atmosphere. Snowflakes collide and generate an electrical charge, producing thunder and lightning. This may explain why heavy snowfall often accompanies these storms—one study found that 86% of thundersnow events produce more than six inches of snow in a single day.^[4]

6 Snow Can Fall in Highly Unlikely Places—Like the Sahara Desert

Snowfall blanketing the sandy dunes of the Sahara—the world’s largest hot desert—may seem impossible, but it has occurred on rare occasions. Spanning 11 African countries, the Sahara is known for its hot, dry climate, with less than four inches (100 millimeters) of rain falling annually in its hyperarid center. However, during winter, the northern reaches of the desert can experience moist, cool conditions that allow snow to fall.

Snowfall in the Sahara was once extremely rare, but it has occurred more frequently in the past decade. In 2016, residents of the Algerian town of Ain Sefra, often called the gateway to the Sahara, were stunned to see snow dusting the red sand dunes. While it’s usually just a light covering, the sight remains striking.^[5]

5 Snow Isn’t White—It’s Translucent

Snow is famously white, especially in popular culture. Yet individual snowflakes are actually translucent. The many facets of a snow crystal scatter incoming light in all directions, diffusing the entire color spectrum and making snow appear white to the human eye.

Because snow is clear, it can sometimes appear blue. As light penetrates deep layers of snow, more red light is absorbed than blue. This is why snow may look white on the surface but blue in deep holes or dense banks.^[6]

4 Snow Can Occasionally Be Naturally Red

Snow can sometimes take on a red or pink hue, a phenomenon known as “watermelon snow.” The color comes from an algae called Chlamydomonas nivalis, which thrives in cold climates. While the algae are naturally green, they produce a red pigment that helps protect them from ultraviolet radiation. Because snow is translucent, the red pigment becomes visible.

Despite its sweet, fruity smell, watermelon snow isn’t something you should eat. While small amounts aren’t dangerous, consuming it can cause gastrointestinal upset. Scientists once believed this algae was responsible for Antarctica’s Blood Falls, but research later revealed the red color there is caused by iron-rich brine flowing beneath the glacier.^[7]

3 The Wind Sometimes Rolls Snow into Doughnut Shapes

Under very specific conditions, wind and snow can combine to create rare formations known as snow rollers, or snow doughnuts. These hollow, cylindrical snow shapes form when wind pushes snow along the ground, rolling it into layers much like a tumbleweed.

For snow rollers to develop, conditions must be just right. Temperatures need to be just above freezing so the snow is soft enough to stick together. The snow must be moist yet light, and the wind speed should be around 30 miles per hour (48 kilometers per hour). Clear ground is also essential, as vegetation can stop the rolling process entirely.^[8]

2 The Largest Snowflake Ever Reported Was More Than a Foot Wide

Most snowflakes are small, but unusually large flakes have been reported. On January 27, 1887, a storm in Montana’s Clark Fork River Valley reportedly produced snowflakes “larger than milk pans.” The largest was said to measure 15 inches (38 cm) wide and 8 inches (20 cm) thick.

However, these claims were never verified, and scientists note that the term “snowflake” can be misleading. What people often describe as giant snowflakes are usually clusters of snow crystals stuck together. True snow crystals are much smaller. The largest confirmed snow crystal was photographed in Ontario, Canada, in 2003 and measured about 0.4 inches (10 millimeters) across.^[9]

1 It’s a Myth That No Two Snowflakes Are Identical

It’s often claimed that no two snowflakes are exactly alike, but this isn’t entirely true. In 1988, Nancy Knight, a scientist working at the National Center for Atmospheric Research in Colorado, discovered two identical snow crystals while examining samples from a Wisconsin snowstorm.

Identical snow crystals have also been produced in laboratory conditions, where growth can be carefully controlled. Given that an estimated septillion snowflakes fall each year, it’s likely that many identical snowflakes have fallen without ever being observed.^[10]