One of my bf's testicles is hanging very low and is a bit sore. says they aren't elevated, so not torsion, and it isn't severe. it's also been really hot (80s) here. what's going on with his testicle?

Hard to say.: Hanging low is not necessarily anything to be worried about - there is always some asymmetry of the testicles and this can change with the temperature. Mild pain in the scrotum - or even testicle - testicle can be caused by a large variety of things including repeated minor trauma or infection. If symptoms are worsening or persistent he should see someone.