You probably just need to top off the recovery tank. When the car is cold, the coolant gets pulled back into the radiator, and drops the level in the recovery tank where the sensor is. Once you are up to operating temperature, the level rises and the light goes out.
its not ever that high, no matter what temp it is its always around full cold. when i first got my car i took it and had new oil put in, radatior flush, new coolant, and new trannie fluid. so they should have filled it up. should i jsut go buy some coolant and dump it in there? i dont know whats going on though because even on 93 octane the car still runs tick lower than half on the water temp, it runs so cold on 87 when i bought it from the guy and i run 89 and it right about where i want it so overheating isnt a possibility.