MYRTLE BEACH, SC (WMBF) - As the heat index climbs above 100, the temperature reading on your car's dashboard will likely show an even higher, and inaccurate number. The temperature is actually coming from a tool called a "thermistor." Instead of a normal thermometer which uses mercury, the thermistor tracks the change in the heat based on the electrical charge that temperatures cause.
Thermistors are actually very accurate, but the reading in your car is usually inaccurate because of WHERE it is placed. With the thermistor on most cars underneath the hood of the front of the car near the grill. According to meteorologists at the Washington Post, this placement allows for heat to be "re-radiated" from the blacktop and asphalt road surfaces.
This added heat raises the number shown on your dashboard. On average, most people notice about a 10 to even 15 degree addition. The sunlight plays a role in this as well. Days where the car is in direct sunlight have higher numbers than cloudy days or nighttime. If your car is stuck in traffic along US 501 or US 17 Bypass, it's likely that you'll get a higher reading than if you're moving faster.
Scientifically speaking, dark surfaces absorb heat through the day, making parking lots a hot spot. This will also cause bank signs to give off an over dramatic temperature too, if the sensor is located in direct sun or close to the asphalt. In contrast: brighter colors tend to reflect the heat, which is why it's suggested to wear bright clothes to keep cooler in the summer.
The actual temperature data from the National Weather Service comes from the nearest airport. These official thermometers are above grassy surfaces in the shade so the numbers are not artificially adjusted.
The WMBF FIRST ALERT Weather App is a way to see the actual temperature and heat index outside, as well as track them hour by hour. Download it FOR FREE today!