The Collaborative International Dictionary of English v.0.48:

Hotness \Hot"ness\, n.
   1. The quality or state of being hot.
      [1913 Webster]

   2. Heat or excitement of mind or manner; violence; vehemence;
      impetuousity; ardor; fury. --M. Arnold.
      [1913 Webster]

WordNet (r) 3.0 (2006):

hotness
    n 1: the presence of heat [syn: hotness, heat, high
         temperature] [ant: cold, coldness, frigidity,
         frigidness, low temperature]
    2: a state of sexual arousal [syn: horniness, hotness, hot
       pants]
    3: a hot spiciness [syn: hotness, pepperiness]