I tried years back to rig an OAT (Outside Air Temp) gage and gave up because of wild variations, always upwards, indications. Concluded that sensor location must be remote of display and sensor location must be established with testing to minimize error. °C bigger than °F but only 2°C is pretty good! Car OAT gages are really good! If the car guys can do it right then we should be able to do it better!