What must happen for mist, smoke, or haze to be recorded in column 9?

For mist, smoke, or haze to be recorded in column 9 of the weather observation report, it must occur both at the observing station and at the time of observation. This requirement ensures that the conditions being reported are relevant and accurately reflect what is currently happening in the immediate area of the observing station.

Visibility conditions such as mist, smoke, or haze that affect how the environment appears at that specific location are crucial for pilots and other users of the weather data. Reporting these phenomena accurately and only when they are present at the time of the observation ensures that the information provided is timely and applicable to immediate flight operations.

In this context, visibility reductions or other conditions might be acknowledged, but without the requirement for the phenomena to be present specifically at the observation time and location, the data could be misleading for navigational purposes.