Jeep Repair: a/c not cold in stop and go traffic, grand cherokee limited, rush hour traffic

Question
I own a 96 Grand Cherokee limited. There are two things that happen when my AC is on and im stuck in either rush hour traffic or slow moving traffic(35mph or less). First the air becomes warm, then the temp gauge starts to move up. If i continue driving the truck it starts to overheat. I also notice that the engine power is not what it normally is. I had a mechanic check the system out and he said everything checked out ok. He suggested to have new freon added. Still does the same thing. Please help!Thank you

Answer
Your mechanic is crap then. Any one thats knows anything about cars,trucks,anything  knows that the ac and cooling system are different. Do u have a 4.0 or 5.2?   check the rad fan  if the coil inside the fan can not move enough air  then u will over heat in traffic. Or u have a low flow in the radiator it self.
See what color the coolant looks like  green or brown  and if there is mud in there.