What does "NM" represent when following a visibility figure in a METAR?

In a METAR report, "NM" stands for Nautical Miles, which is the unit of measurement used for visibility. The use of nautical miles is particularly relevant in aviation, as it aligns with the navigation and operational standards of air traffic control and navigation systems.

Visibility is a critical factor for pilots, impacting their ability to take off, navigate, and land safely. When a METAR indicates visibility followed by "NM," it informs the pilot about the horizontal distance they can see, enabling them to assess the suitability for flight operations.

The other options do not apply. While weather conditions are described in different sections of a METAR, they do not influence the abbreviation "NM" used in visibility reports. Statute miles, although a common measurement in other contexts, are not used in METAR visibility reporting. Inches, typically related to rainfall measurements or other conditions, are not relevant to visibility at all.