If your carpets are dry, the first thing to look is the cabin (polen) filter. If it is clogged, you just can't demist the windows (it happened to me). You will determine it it is clogged like this:
Set the fan to 3 and to blow directly towards you and put your hand on the grill where the air is coming out. Now set to recirculate, wait a sec and then see if it makes any difference in amount of air. If you have more air on recirculate, then your cabin (polen) filter is clogged and needs replacing. It is really easy to replace, 1min. Hope this helps. Now it wan't mist as bad (even if you don't turn ac on). And ac does not turn on below +5C anyway.