re: Car- Outside Temperature Indicator

Part of the reason is because it’s not actually a standard thermometer, it’s something called a thermistor. A thermistor measures the change in electrical current as a result of heat added or removed, rather than directly measuring temperature. It’s usually pretty accurate… except when you mount it in a car engine where it is exposed to re-radiated heat from the asphalt surface. That makes it read a higher temperature than it actually is because the re-radiated heat gives a higher reading since the thermistor is based on the electrical current.