Depends upon the KIND of hug
Yes, obviously a hug is kino. Any body contact that's not blatantly inappropriate will warm a gal up.
Eyecandie's got the idea. I'll add a bit here:
If she gives you one of those light, quick, "girly hugs," in which the first thing she does is quickly turn her head to avoid a kiss, she doesn't have much interest at the time. The disinterested gals minimize the extent and duration of body contact so as not to get those hormones flowing.
On the other hand, if she gives you an "attack hug," in which she's sqeezing the juice out of you, chances are that's exactly what she's trying to do. If she grinds her breasts into you, or gives you an unexpected kiss, she's really hot for you. Green light!
If you think to, you can fan the flame a bit more by maximizing leg and foot contact and stroking her hair in the back of her neck as you hug. The back of a gal's neck is a real hot spot!
Pull away before she wants to end the hug -- without rejecting her -- just ending it a little bit before she does -- and it'll up the intensity of her desire even further.