Your are right, I am not an expert on it, but I think it is inaccurate in the minus not in the height, meaning that it gives less than the actual degree. ✌️
Actual temperature readings are always taken in controlled enviornment, not in the open. Try it yourself by keeping your car in sunlight & next day in shade at the same time 😁 Road temperature is always higher as asphalt absorbs heat.
