# How can frozen clothes dry overnight?

I put some wet Polyester clothes outside for the night (the clothes were washed by hand with pretty cold water -maybe around 4°C- and wringed by hand so there was still water dropping of them when I put them outside). It was -4°C went I put them. One hour later I checked the clothes and they were totally frozen. In the morning (before sun rise) the clothes were dry : it was -6°C. The sky was clear (almost no clouds) and there was no wind.

I am quite surprise that my clothes can dry in less than 10 hours with such a low temperature. This answer explains that the process is called sublimation but it doesn't explain where does the energy needed for the water to sublimate comes from ? In my case there was no sun, no wind, no temperature above 0°C.

Put thermodynamically, a process occurring at constant temperature and constant pressure is driven by minimization of the Gibbs free energy $G=U-TS$, where $U$ is the internal energy, $T$ is the absolute temperature, and $S$ is the entropy. There's a tremendous entropy increase associated with an ice molecule leaving its rigid structure and entering the relatively low-humidity atmosphere, where there are many more potential configurations. This large value of $S$ is what drives solids and liquids to have a nonzero vapor pressure at nonzero temperatures even if their temperature is insufficient for boiling. In general, all condensed matter around you is evaporating/sublimating, although the rate may be minuscule.