Engine Temp Spikes to 240-250 then regulates back to 210

[bmo201656]

I’ve got a 2017 Silverado with the V6.

 

I noticed the other day that the radiator fan was still running after I turned truck off and got out. Since then I’ve noticed that here and there, as well as the temp getting up to ~240 degrees before regulating back to 210 (averaged).

 

Thermostat was replaced in September and no problems with it since then. Anything else ring a bell on what could be happening? 

[BigBadSierra]

I think that's the range it has to hit before the thermostat opens and cools the trans back down.