Overheating causes high idle, normal?

[tudorv]

Hi! I'm back seeking more advice from you guys. PLease help me out if you can.

My GZ runs fine now. No real issues with it and I keep putting miles on it. There's just one thing bothering me. After riding for a while (so the engine is all warmed up) if I get stuck in heavy city traffic, in full sun, with sitting cars all around me, after a few go-stop-go-stop routines, the idle gradually increases up to a pretty high rpm. And then it stays like that. (unless i fiddle with the idle screw)
After I get away from the traffic jam and give the engine a chance to cool down, the idle returns to normal.

Should this be happening? If the engine overheats, and the rpm increases, won't that make it overheat even more?

What do you think I should do?

Thanks!