[Karsten (OP)]

Why does snow squeak when it is really cold? It squeaks when you walk and it squeaks when you drive on it. Not powdered, fluffy snow - the compressed stuff on the side walks and streets. Is it complaining?

[RD]

Air trapped between the snowflakes being rapidly expelled under pressure (of foot/car).

In Antartica the snow becomes increasingly compacted into ice and the trapped air can be entombed for thousands of years in this ice ...

An ice core is a core sample from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods. The composition of these ice cores, especially the presence of hydrogen and oxygen isotopes, provides a picture of the climate at the time.

http://en.wikipedia.org/wiki/Ice_core

[Karsten (OP)]

So why does it do that when it is colder? How does the air get into the snow from one day to the next? One day it is just hard-packed snow, the next day after the temperature dropped, it squeaks. It should have the same amount of air in it.

[Make it Lady]

I thought it might be a property of powder as some types of sand whistle when you walk on them.

[MonikaS]

Why does snow squeak when it is really cold? It squeaks when you walk and it squeaks when you drive on it. Not powdered, fluffy snow - the compressed stuff on the side walks and streets. Is it complaining?

No it's so depressed about being compressed, so it's just groaning... <tiptoeing away>

[RD]

This explanation sounds better than mine ...

If you are a careful observer, you will have noticed that whether snow squeaks when you walk on it depends on how cold it is outside.

When you walk on snow, your boots apply a pressure. If the temperature of the snow is warmer than approximately 14F (-10C), then the pressure exerted by your boot partially melts the snow allowing it to 'flow' under your boot and no sound is made. When the snow is colder than -10C, the pressure from your boot does not melt the snow, and instead the ice crystals beneath your boot are crushed making a squeaking, or creaking, sound.

http://cimss.ssec.wisc.edu/wxwise/squeak.html

[Bass]

Cold snow is much "stickier" on skis and snowboards for the same reason.  Skis glide easily over the snow because the pressure they exert melts a very thin layer of snow, reducing friction at the boundary between the ski and snow.  A good hydrophobic wax helps this process even more.

Cold snow does not melt as readily under the pressure, increasing the friction as the snow crystals come into contact with the ski base.  Below -20F, it's hard to find a suitable wax to make the skis glide.

[Karsten (OP)]

Ah, this makes sense. Too cold and the crystals don't melt but scrape over each other. And, while the question "Can it be too cold to ice-skate?" has never been answered to my satisfaction, it seems it can be too cold for skiing due to not-melting of snow.

At -35C it reasonable to be depressed (when compressed) and groan. []