We just had the first big snowstorm of the year the other day!

Squeaks and I had so much fun playing in it. [Squeaks squeaks] Yeah, that was when we went sledding! We also like to build new things together when it snows, like snowballs, snowmen, or even igloos!

All of that snow is so much fun, and it can completely change the world around us. The ground is covered in a thick, white blanket, and ponds start to freeze over. And there’s another thing that changes.

There are spikes of ice hanging down from the roof of the Fort! These long cones of ice are called icicles, which is a pretty good name for them, since they kind of look like ice turned into a popsicle! Icicles form down from different places where there’s snow.

You might see them growing off of roofs, gutters, and even tree branches. It looks like ice is dripping right off of those trees, doesn’t it? But how do icicles get there in the first place?

Well, just like a snowman, icicles are made out of the snow. But unlike a snowman, people don’t make the icicles — they form naturally. For icicles to form, there have to be two things: snow, and warm sunlight.

See, the snow and the ice in these icicles are made out of the same thing: frozen water. When liquid water gets really cold, like during the winter where we live, it freezes into ice. Usually, we get our frozen water coming down from the sky as snow.

It might seem very different from the hard ice in an ice cube, but the only difference is how the frozen water is shaped. Each snowflake is made up of tiny pieces of ice arranged into a snowflake shape, whereas in an ice cube the little pieces of ice are all packed together. So snow and ice are really made of the same stuff.

After the snow falls, it sits on the ground, on top of branches, and on roofs, and as long as it’s below a certain temperature, that snow will stay frozen. We call this temperature the freezing point. It’s about 0 degrees Celsius or 32 degrees Fahrenheit. [Squeaks squeaks] Exactly, that’s what people mean when they say it’s freezing outside.

They mean it feels really cold — maybe cold enough to freeze water into ice or snow. But even on a freezing cold day, the sun can still come out. And the sunlight is warm!

As the warm sunlight hits the snow, the temperature of the snow starts to slowly go above the freezing point again. What do you think might happen to the snow, Squeaks? [Squeaks squeaks] That’s right, it will start to melt into water. But!

It melts very slowly, and it doesn’t all melt at once. The heat from the sunlight melts the top layer of snow into water, then the next, and the next. But if it’s only above freezing for a short time, something special can happen — like what happened to the snow on our roof.

As the top layer of snow on the roof melted, it rolled down the roof as liquid water, and some of it started to drip off of the roof. But it didn’t /stay/ melted for very long! By the time the water got to the edge of the roof, the cold air around it cooled it back down below the freezing point.

The water stopped in its tracks and froze back into ice, but it wasn’t shaped like a snowflake anymore. This time, the ice was all packed together like in a hard ice cube. That tiny little frozen drop at the edge of the roof became the beginning of an icicle! [Squeaks squeaks] That’s true, the icicles on our roof are much bigger than one drop of ice!

Even though icicles start out small, they can grow. It can take a very long time for an icicle to get big, but eventually, they can get /huge/! As the sun keeps melting the snow, and the cold air keeps re-freezing the water as it drips down, the icicle will start to get longer, and thicker.

More ice will get added, then more, and more, until you have some enormous icicles! Sometimes that takes weeks, but other times, it can happen in just a few days. It all depends on having the snow, the warm sun to melt it, and the cold air to freeze it back into ice. and if all these things work together just right, your roof can end up perfectly decorated for the winter.

Have you ever seen icicles forming? What kinds of amazing things do you think you could build out of frozen snow or ice? Have a grown-up help you leave a comment below, or send us an email at kids@scishow.com.

We’ll see you next time, here at the fort!