What does the abbreviation "RMK" in visibility reports usually signify?

The abbreviation "RMK" in visibility reports signifies "Remark." This term is used to indicate additional information or comments that accompany the observation. When a visibility report includes "RMK," it typically precedes specific remarks that clarify or expand upon the primary data presented in the report. For example, it might provide insights into weather phenomena, observation conditions, or any pertinent details that could affect the interpretation of the reported visibility.

In meteorological practices, remarks can inform users about localized conditions or phenomena that are not captured in standard reporting metrics. Thus, "RMK" serves as an essential tool for meteorologists and surface weather observers to communicate these additional observations effectively.