Engine temperature increases in traffic on 1994 Oldsmobile Achieva

The engine runs at normal operating temperature (about 195 degrees) while on the highway. When I stop at traffic stops the engine temperature increases from 195 degrees to over 220 degrees then returns to normal when back on the highway. I have had the thermostat, radiator fan motor & radiator changed. I have had the engine and coolant expansion tank cleaned & flushed. The engine runs good and there is no indication that the head gasket is blown. The first time this happened almost three years ago, changing the fan motor resolved the problem. What else could be causing this heating up to occur?

Asked by for the 1994 Oldsmobile Achieva
It would be good to know whether the fan runs or not. Without that essential piece of knowledge, I can't tell you much.
Please remember to diagnose before replacing parts. You can't be successful without diagnosis.
If you want to find an Olds specialist, here's our directory link for you:
The fan runs all the time when the air conditioner is on. The a/c is on when the temperature increases in traffic. Turning off the a/c makes no difference. My mechanic told me that the fan comes on when the coolant temperature reaches 229 degrees, if the a/c is not on. He could not tell me why the temperature increases in traffic the way it does. Evidently he thinks that this is normal.