When does frontal fog usually dissipate?

Frontal fog typically dissipates as the front moves and clears the area. This phenomenon occurs because frontal fog is associated with the lifting of warm, moist air over a frontal boundary, which causes condensation and the formation of fog. As the front progresses, the air mass changes, often resulting in drier and more stable conditions, which leads to the dissipation of the fog.

When the front passes, the temperature and humidity conditions shift, allowing the fog to evaporate. The clearer air mass that often follows a front helps to improve visibility and dissipates the moisture that was contributing to the fog.

In contrast, the other options do not accurately describe the typical behavior of frontal fog. For example, while temperature drops at night can lead to fog formation, they do not directly cause the dissipation of frontal fog. Increased humidity levels might actually worsen fog conditions rather than improve them, and heavy rainfall usually does not occur after the development of frontal fog, as they are generally linked to different meteorological scenarios.