Why laundry dry up also in cold/frost? Why laundry dry up also in cold/frost? When you have frost, water in the clothes should freeze, but if clothes are dry, then it should be possible that steam in the clothes does not have time to freeze.
 A: It is called sublimation. It is how ice cubes disappear in the freezer.

Snow and ice sublime, although more slowly, below the melting point temperature. This allows a wet cloth to be hung outdoors in freezing weather and retrieved later in a dry state. I

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Sublimation is the process of transformation directly from the solid phase to the gas phase without passing through an intermediate liquid phase. Sublimation is an endothermic phase transition that occurs at temperatures and pressures below a substance's triple point in its phase diagram

A: 
Why laundry dry up also in cold/frost? 

Probably because, initially, the clothes and the liquid water trapped in the clothes fibres, are both at a temperature well above 0 C. 

When you have frost, water in the clothes should freeze, 

And it does, when the temperature of the garment and water trapped within it have eventually reduced to below 0 C 

but if clothes are dry, then it should be possible that steam in the clothes 

If clothes are already dry, the situation is not relevant to your question of how (wet) clothes become dry (or dryer) when air temperatures are below 0 C.

it should be possible that steam in the clothes does not have time to freeze.

If you move warm wet clothes into a cold environment for a sufficiently short time, the water will indeed not have time to freeze. The temperature of the majority of water will not be sufficiently reduced.
Left longer in air at a temperature below 0 C the liquid water in the clothes will freeze and any water vapour in the clothes will form frost.
