A sensor detects the temperature outside of the car.
If the car has been stationary, the gauge may display a temperature reading that is too high.
When the outside temperature is within the range -5 °C to +2 °C (23 till 36 °F) a snowflake symbol is also shown in the driver display as a warning for potentially slippery conditions.
Change the unit for the temperature gauge via system settings in the centre display top view.