What is indicated by "SMK" in a METAR report?

In a METAR report, "SMK" stands for smoke. This notation is used to indicate the presence of smoke in the environment, which can affect visibility significantly. When observing a METAR, it's essential to recognize that "SMK" directly relates to the conditions that might impair visibility, particularly at airports and other operations where clear visibility is crucial for safe air traffic.

The presence of smoke can be due to various factors, including wildfires, industrial emissions, or other sources. It’s vital for pilots and air traffic controllers to understand this condition as it can have safety implications during takeoff, landing, and ground operations.

The other options do not correspond to the "SMK" designation in a METAR report. For instance, humidity levels are typically discussed in different measurements, and severe weather is indicated by specific codes or terms rather than "SMK." Strong winds are also represented in a distinct format within the METAR structure, not by the smoke indication. Hence, the choice indicating smoke accurately reflects the meaning of "SMK" in meteorological observations.