How are temperature and dew point expressed in a METAR?

Temperature and dew point in a METAR are expressed in degrees Celsius. METAR reports follow international aviation standards set by the International Civil Aviation Organization (ICAO), which mandates the use of the metric system for temperature. In addition to this, temperatures and dew points are reported to the nearest whole number, rounding down if necessary, providing pilots and meteorologists with crucial information for flight operations and weather assessments.

The other options vary from temperature scales that are not used in METAR reporting, like Fahrenheit and Kelvin, to a concept that is not applicable to changes in temperature measures. Therefore, the clarity and uniformity provided by reporting temperature and dew point in degrees Celsius supports effective communication in aviation meteorology.