Since childhood we have known a folk omen - "If the snow squeaks underfoot, the frost will be even harder. Have you ever wondered why snow squeaks at all? The snow cover is made up of many snowflakes, ice crystals. But there is a lot of air between and within these crystals, or to be more precise, about 95% of the total volume of snow is air.
When we step in the snow, the air is squeezed out, and the snowflakes rub and break against each other, making a very faint, almost imperceptible "squeak". But because there are so many snowflakes, these barely audible sounds merge into one louder one, which is what we hear as a sure squeak.
"But it's not always the snow that squeaks," you'll say, and you'd be right. It turns out that with a little frost, the surface of snowflakes is covered with the thinnest layer of water. As the frost increases, this layer decreases, and at -10 C the thickness of the water layer is only one molecule, while at -1 C it is hundreds of times greater. It is the layer of liquid water on the surface of the snowflake crystals that drowns out the creaking in light frost. In addition, the constantly changing water layer on the surface of snowflakes causes snowflakes to "stick" together.
Freshly fallen snow is very fluffy, it has weak bonds between the crystals, and the snowflakes freeze together, and their destruction generates a slightly different sound - a lower, rustling sound. That's why the crunch of frozen snow can be heard even in light frost.