"Official" (Weather Service) temperatures are measured in a shaded instrument shelter under standard conditions. Almost regardless of where the sensor is (I don't know)if you have the truck parked in the sun it could read considerably higher than "official." Also, a lot of commercial electronic thermometers just aren't calibrated very well to start out with, and never get re-calibrated, so they can be off by a considerable degree. They aren't inherently inaccurate, they just don't get set and reset properly.