Coolant Temp alarm after carwash

[Bret11]

I got gas this evening and then went thru the automatic car wash at the station. I put it in neutral and left the engine running as we went through. Almost immediately after leaving the car wash, I got a high coolant temp alarm and the temp gauge was in the red. I parked it right away and turned the engine off.

Under the hood it was warm but there was no apparent catastrophe. There was a soft hiss coming from the radiator, but that didn't seem like anything extreme. I couldn't find any obvious failure and my mechanic's shop was closed, so I decided to let it cool down for half an hour and took my daughter to the playground. When we got back I turned the ignition to the on position to check the temp on the gauge and it was right in the middle. We weren't far from home so I decided to give it a shot at making it back. The temp was steady and right in the middle all the way home. At home I let it idle for a few minutes with the AC on -- the needle stayed steady.

So it appears that I have no overheating issue?

Is it possible that some water from the carwash got under the hood and was heated by the engine which tripped the coolant temp alarm?