hmm... the locked glovebox is not well concealed as much as water liquid/vapor is concerned
cold winter air is not dry, not in terms of relative humidity anyway, it's the hot winter air that is dry.
it's not just condensation that affects electronics at low temperature... when the temperature is low, the physical property of metal changes dramatically, makes it rather... crispy... also some lubrication inside of the harddrive might even freeze at low temperature, which could do some serious damage to the harddrive among other parts...
but i don't think 20F/-5C is gonna be that serious... condensation wise, if you are concerned about that, put your ipod in a ziplock bag or something (are you using the control of the ipod or the control on your dashboard?)