What does a visibility reading of "2 1/2 SM" translate to?

A visibility reading of "2 1/2 SM" translates to a visibility of 2.5 statute miles. In METAR reports, visibility is commonly expressed in statute miles, and the format "2 1/2" is a fractional notation that equates to 2.5 when calculated. Therefore, the reading provides a clear indication of how far one can see, which is crucial for pilots and other aviation personnel in assessing safety conditions for flight operations. This reading does not inherently suggest any weather phenomena like fog or rain; it solely measures the distance at which objects can be clearly discerned.

The other options imply specific conditions or alternative measurements that are not directly related to the straightforward visibility indicated by the METAR reading.