What can affect visibility in weather observations?

Visibility in weather observations is significantly impacted by the presence of phenomena like fog, rain, or snow. These conditions introduce moisture and particulates into the atmosphere that directly obstruct the ability to see clearly over distances. Fog can create a thick layer of moisture that reduces visibility to very low levels, while rain and snow can lead to reduced contrast and visibility due to the scattering and absorption of light.

Cloud cover, while it can affect how much light reaches the ground and influence overall visibility, does not typically obstruct the line of sight in the same way that fog, rain, or snow does. Temperature can affect relative humidity and could indirectly lead to conditions like fog, but it does not directly reduce visibility by itself. Wind direction might influence local weather conditions and potentially disperse fog or precipitation, but it does not directly affect visibility in the same manner as fog, rain, or snow. Therefore, the presence of these weather phenomena is the primary factor in significantly impairing visibility during weather observations.