In a METAR report, what does "SM" indicate?

In a METAR report, "SM" indicates prevailing visibility, which is a critical measurement for aviation safety and operations. The term "SM" stands for statute miles, a unit used to quantify visibility in the United States. When included in a METAR report, it demonstrates how far a pilot can clearly see, which is essential for takeoff, landing, and in-flight navigation.

Visibility readings are vital for determining whether weather conditions allow for safe flight operations. Good visibility generally means the flight can proceed as planned, while reduced visibility may require pilots to adjust their approach, consider instrument flight rules (IFR), or delay operations until conditions improve. Understanding the implications of visibility measures like "SM" is fundamental for effective flight planning and safety.