Thermostat getting hot for no apparent reason

You mean the temp gauge rises. May need to bleed the air out of the cooling system. Make sure your fans are working. If it persist then have test ran to confirm or rule out a head gasket failure. Block check test for exhaust in the cooling system. Compression test is done also to confirm compression leaking, May see steam exiting tail pipe is another sign or bubbles in or boiling coolant. I would for check the fans first and do a bleed on the cooling system to rule it out.

Hey, similar situation it happened on my GMC Acadia 2012 it was overheating in local but on highway was pretty good. Even that the fan was working after the engine was off for couple minutes or so. Also,the AC Shut off light up on dashboard when the ac was working. Just took my vehicle to the dealer and everything was ok no leaks. The only reason was the lower fluid in the radiator! I couldn't find the radiator tap just saw the coolant storage and it showed full but the dealer filled radiator coolant without any charge and my vehicle is working perfect. Just be cautious mechanics take advantage from simple things to cover their expenses is really hard to find honest mechanics now in days. Good luck.

Check both fans are working. Mine only had one fan working. Mine had one fan working the whole time. It was the one that turns on when the a/c is on. So it was running fine when days were not to hot but on 100 degrees and up it would over heat. Then I checked and the other fan was not working.

I had exact the same problem that Pilotman27 had on my 2012 GMC Acadia, checked my radiador and the coolant fluid was low- added fluid and it’s working perfectly I hope this will help someone.