Something I Vaguely remember is that Heat/Warmth is sign of good blood circulation in the area, and that is often associated with growth when on NBE.

before some of you start doubting your progress, you may want to consider this. When I was on pharmas, and getting good growth up to a B+or so, this temperature difference did not occur. The growth I have experienced recently, and more rapidly than I expected, has been a different kind of growth. This time it rather felt as if I could feel a pair if implants against my chest. Very firm. It wasn't like before, when it was more of a large mass behind my nipple area, and softer flesh making up the rest. It was the heat that accompanied this growth that has been noticed, and made me wonder.

So, if you're not "feeling the heat", don't worry. That will probably come at the right time, should you take it that far.