As Denny mentioned, ambient temperature and internal temperature usually do not match during active fermentation because, to use a big word, fermentation is exothermic. The little yeasty beasties are reducing polysaccharides to monosaccharides and monosaccharides to carbon, which they transform into energy. That process releases heat. I remember watching a series of videos on VHS tape that were created by Micheal Jackson (the beer hunter, not the singer) where he was in a fermentation room at a German brewery. What was interesting to see was that there was frost on the outside of the fermenter, but fermentation activity appeared to be very strong.