Snowy Days

Core Idea

Snow falls when the air is cold enough for water in clouds to freeze into ice crystals instead of forming liquid raindrops. Snowflakes are tiny ice crystals that stick together as they fall. Snow covers the ground in a white layer, makes the world quieter, and eventually melts back into water when the temperature warms up.

How It's Best Learned

If possible, let children catch snowflakes on dark paper or mittens and look at their shapes. Compare snow to rain -- both come from clouds, but temperature decides which one you get. Bring snow inside in a cup and watch it melt to reinforce that snow is frozen water.

Common Misconceptions

• Snow is different from rain. Snow and rain are both water from clouds -- the only difference is temperature.
• It has to be exactly 0 degrees to snow. It can snow at temperatures slightly above freezing if the air higher up is cold enough.
• Every snowflake looks like a perfect star. Snowflakes come in many shapes; the classic six-pointed star is just one type.

Explainer

You already know that rain falls from clouds when water droplets get big and heavy enough to drop. Snow works the same way, but with one big difference: temperature. When the air is cold enough -- usually at or below freezing (0 degrees Celsius, or 32 degrees Fahrenheit) -- the water in clouds does not form liquid droplets. Instead, it freezes into tiny ice crystals. These crystals stick together as they fall through the cold air, and by the time they reach the ground, they have become snowflakes.

Snowflakes come in many shapes and sizes. Some look like tiny six-pointed stars with beautiful patterns. Others look more like simple needles or flat plates. No matter what shape they are, all snowflakes are made of the same thing: frozen water. If you catch a snowflake on your mitten and look closely, you can see its shape. If you hold it too long, your body heat will melt it right back into a tiny drop of water.

When snow piles up on the ground, it creates a white blanket that covers everything. Snow is white because the ice crystals reflect light in all directions. A snowy landscape is also quieter than usual -- the fluffy snow absorbs sound instead of bouncing it back. That is why the world feels peaceful and hushed after a fresh snowfall.

Snow does not last forever. When the air warms up, the snow melts and turns back into liquid water. This water soaks into the ground, flows into streams, and fills rivers and lakes. In places that get lots of snow during the winter, the spring snowmelt provides water that plants and animals need for the rest of the year. So snow is not just frozen rain -- it is a natural way of storing water until warmer weather arrives.