[Tidewater BE]

A good rule of thumb is to expect tire pressure to change 1 lb for every 10 degrees of temperature change. I too check mine in the morning on cold tires and set the pressure per the door tag. The minor differences in variation during the day as the ambient temperature rises isn't worth worrying about. But my truck stays outside. My method may not work as well if I kept the truck in a heated garage with a potential temperature difference of 30-40 degrees. Check out the link below for Tire Rack's recommendation on accounting for variables.

Tire Tech Information - Air Pressure: When & How to Set