CHARLOTTE, NC (WBTV) - And yes, so is the thermometer at the bank that you may drive by on your way to work. And the thermometer you have hanging on the side of your house on your back deck. We know, we get several pictures of these thermometers every time we go through a heat wave. They always seem to be running about 5-10 degrees hotter than the actual air temperature reported at our official weather station. So why is this?
These thermometers are highly influenced by their immediate surroundings, which very often skews them towards a higher (hotter) reading. For your car, the heat from the asphalt and your car engine heats up the air directly around the sensor more than the outside surroundings, so it's an inaccurate representation of the overall temperature.
Bank thermometers often have sensors on their roofs, which, being black, also heats up more than the immediate surroundings. So while yes, the air immediately surrounding the sensors in these areas may be that hot, it's not a fair representation of the uniform temperature across the area that most of us are experiencing.
The same can be said for the thermometer you have in your garage, on your porch, or on your back deck. So then, where the heck DO accurate temperature readings come from!? Well, there are certain measures that have to be taken when considering the placement of a thermometer in order to ensure an accurate reading.
For official weather observing stations, the sensors are solar-shielded and are located at least ten feet away from trees, fences, buildings, concrete and asphalt to make sure there isn't any re-radiated heat. The weather stations are placed on a pole about five feet above the surface, mainly on grassy surfaces or dirt. This way the National Weather Service has a set standard for the location of a weather station, which helps improve the overall accuracy of weather reports.
So next time you are wondering why we are reporting a temperature of 99 in Charlotte when your car is reading 108, just remember, that 108 only represents the air DIRECTLY surrounding your car thermometer, which is heated extra due to additional heat from your car's engine and the black asphalt!