Odd temperature behavior

sounds like the thermostat is the problem again

You have a sticking thermostat. It will shortly completely fail causing a constant problem. Bite the bullet for a new one ASAP. I have also seen a bad rad cap do this if it is dumping pressure suddenly. Both are much cheaper than an engine.

Lugnut

Thanks for responing.

With a warmup over the last few days, the temp gauge operation has gone back to normal. Maybe the extreme cold temps had an effect. I'll continue to watch the gauge. But as long as I don't see it go higher than normal, I should be OK.

It may be that in the warmer weather, your stat is not closing as tightly allowing it to respond more normally during warmup. It is likely that it will eventually start to stick even in warmer weather. The problem is that the stat is sticking closed until the temp goes beyond the calibrated position causing the engine to heat too quickly before it snaps open. Keep in kind that the temp sensor on your engine may be past the stat position which means the engine may be overheating even before the guage will show overheating if the coolant is not actively flowing as would be the case with a stuck stat.

Lugnut