overheating should mean that your gauge is reading well passed the 90 mark. the car should run just short of 90 when running nicely and if you sit in traffic or are on a really hot day should just justed passed 90 before the fans kick in and bring it down. if its going more than a little bit passed 90 thats when your running hot and overheating.
this usually happens because the fan speed resistor breaks down and means the fans stop working all together. if you have the diagnostic software for your car then you can run a fan speed actuator test to see if it works.
you can also check the electrical component itself using a multi meter to see if it still works. when my resistor failed on me I took it out and you could see the wire had split on the resistor so it was obvious it had broken. if it has or you suspect it has broken take a peice of wire, solder or crimp some connections on there real quick and short the connector for the fan speed resistor. literally just shove the connections in the plug to short it. this changes the fan so instead of being low and then high speed it will run straight into high speed mode when the low speed has triggered, so you won't overheat, although its not ideal it will stop you from overheating until you get the resistor replaced.
if the resistor is fine then I would look at the radiator next, as David suggests. run your finger down the inside edge of the rad and see if it feels really soft and crumbly. if it is then your radiator is shot and will need replacing.
also have a look at your running temperature normally. if your car is running somewhere between 50 and 70 normally then the stat is also shot, if the radiator is shot then the stat is usually shot as well and replace them at the same time whilst you are doing it, its easier.
let us know what you find.