Does the temp come back down on its own or does it keep going up until you start moving again? Mine started doing that and I found the cooling fan in front of the radiator wasn't coming on because the electric motor was fried. I got to the house one afternoon with the temp registering about 220, raised the hood and the fan motor was almost on fire! If you temp is going up and coming back down on its own while sitting still...don't worry about it, but if it goes up and won't come back down until it gets airflow from driving...check the cooling fan. BTW...it ran me $235 from Ford! Can probably do better, but I wanted a factory part for that. Sorry about the length!!!