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It’s summertime and the temperatures are rising all over the country. If you check your car’s “outside temperature” reading on the instrument panel, be prepared to see some triple-digit numbers. However, don’t be too surprised if the car’s outside temperature reading is 111 degrees Fahrenheit when the weather app on your phone says that it’s only supposed to be 95 degrees today. But why is the outside temperature gauge so inaccurate?

Why is my car showing the wrong outside temperature?

The temperature reading on your car’s instrument panel or dashboard isn’t coming from a thermometer; it’s coming from a thermistor. A thermometer uses liquid mercury that expands and rises toward a certain value when heat is added (hotter temperatures). It then contracts and lowers when heat is removed (colder temps).

According to the Weather Channel, “A thermistor, on the other hand, measures the change in the electrical current as a result of heat added or removed.” That said, it’s not the thermistor itself that is inaccurate. In fact, thermistors give accurate temperature readings, but the issue is where your car’s thermistor is located.

Most automakers place the car’s thermistor in the front bumper near the grille, which allows it to pick up heat from the asphalt. This is why your car’s outside temperature reading will read higher when the car is in the garage or stopped at an intersection. It’s picking up the heat from the hotter asphalt.

When are the car’s reading most accurate?

A car driving down a snowy road.
A car driving down a snowy road. | via Getty Images

The car’s thermistor is the most accurate at nighttime since it’s not picking up heat from the asphalt as much. It’s also more accurate on a cloudy day and when traveling at higher speeds. Also, if you think that the inaccurate reading isn’t a big deal, it can be during the winter months.

For example, if the temp gauge reads 34 degrees while you drive down a snowy road, but it’s actually below freezing, that could mean there is black ice present without you knowing.

How can you get an accurate outside temperature reading?

An aftermarket external car thermometer
An aftermarket car thermometer | via Amazon

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If you really want to know what the outside temperature is when you’re driving, you may be better off looking at the weather app on your phone. Official temperature readings are taken from six feet off the ground and over a grassy area, so the temps you can get from the National Weather Service are more accurate.

If you prefer to have an actual reading in your car, we suggest getting an external thermometer that you can connect to your car. It may seem excessive, but there are plenty of aftermarket thermometers for less than $20 for sale online. They’re also very easy to install.

That way, the next time you see that it’s 111 degrees outside, it probably really is. In that case, you may want to park your car in the shade. Check out these five garage alternatives for storing your car.