Engine over heating

I got a '95 sunfire that the coolant light keeps coming on and goin off, and the temp will get really high and then at times drop decently low. Now if I'm on the freeway it doesn't get warm at all but if I'm in town it will over heat within a few minutes. What could be the problem???? I need to know what to replace.

My 98 does that once in a while, flush the system and put in new coolant, change your thermestat. There are alot of things you can do.
If I am just going to be touring in town, I pop my hood...worked till I flushed the system and solved the problem, Thermostat was on its way out the door too.

check to see if there is coolant in the radiator.