Most weather sensors in big cities are at the major airports. Based on your reply, all temperatures taken from airports are invalid because they will be "too warm"??
As many here pointed out, the location of the sensor at KEWR is sandwiched on a strip of land with a runway on one side and a canal on the other side. Perfect location? No, but it could be worse!
If the "official" Newark temperature was taken from downtown Newark (more asphalt), the air temperature in my opinion, could be even warmer than it's location at the airport.