Any idea why my engine temp gauge would all of a sudden become sensitive to a cold climate? I live in Florida and we see very few cold days but lately it's been fairly cold (40-60). If I'm on the highway, the engine temp never reaches dead center on the gauge. Only after a good amount of city stop and go does it reach center and even then regular driving cause the temp gauge to drop again.

This has only started to occur, I've had the car 6yrs +

I've replaced nothing lately but my water pump and thermostat we're replaced at 75k. otherwise, the cooling system is stock. im at 110k now.