moisture getting inside car and freezing on back windo

[monroegt]

Hey guys I just got my 96 mutang gt like 3 weeks ago when I went to pick it up it was frozen shut on the inside. I thought it was just because we had a realy warm week and then a cold one. So I let it go and put it in the garage but I have noticed that when I am driving and park the car for about a hour or so my rear and left front left rear windows are frosted over. My guess is that i have a case of some bad wheather stripping but i can't find where at it would help a lot if any of you had a good guess at all! thank you very much in advance

monroegt