All the suggestions on the radiator are good thoughts. I should have given more information. When I got the car 7 years ago it had an issue with overheating even when moving. I replaced the radiator with a new one. While the radiator was out, I pulled the water tube for a good cleaning. It was in acceptable condition so it went back in. Also pulled a lower Welch plug and flushed the block. Lots of “mud “ was removed. Since then I’ve not had an issue. While I have only done a couple of parades, no problem until today. As a side note, I had a different Welch plug spring a leake a few months ago and when I replaced it I took the opportunity to flush the block again. Very little “mud flushed out that time. Could it be and issue with the vanes of the water pump have corroded and not enough water is being moved at idle? Maybe, it appears to be the original. The car only has 82k on the clock. The fan pully appears to be original as well as the fan. The question about the electrical fan was a thought that would be an easy route without having to replace the pump.
I am definitely open to all suggestions