i'm no met, and I do have a crappy ambient weather weather station on wunderground. I know it runs warm based on where it is placed, and i am sure that the rain guage isn't terrible accurate. you know what-I don't care. it gives me an idea of what is going on at my location.
If others use that for "accurate" data, i don't really give a crap. For fully accurate data, go to the closest ASOS.