Pontiac Repair: Temperature gauge, coolant level, pontiac grand prix

Question
1995 Pontiac Grand Prix  3.0 engine size

After driving 70 mph for about 20 miles when I stop at a stop sign the temperature gauge starts to rise. It hasn't overheated yet. As soon as I start traveling again the temperature returns to normal. Driving in town has no effect on the temperature. The termostat was replaced about 3 years ago.  

Answer
If its not overheating, you dont have a problem. But you should check the coolant level and condition. If it is low or dirty and weak, flush the cooling system and fill with new Dex-cool.
If its not getting hot while driving in town, your fan is obviously working.