Which visibility restriction is considered the most frequent and troublesome?

Fog is often considered the most frequent and troublesome visibility restriction because it can develop quickly and cover large areas, significantly reducing visibility. When fog is present, it can create dangerous conditions for navigation, particularly for boats and ships on Lake Ontario, where clear sightlines are crucial for safe passage. The density of fog can vary, and in some cases, it may reduce visibility to less than a few meters, making it challenging for operators to see navigational aids, other vessels, or hazards.

Unlike thunderstorms, which can be localized and may provide some advance warning, fog may appear suddenly and linger for extended periods. Additionally, conditions such as calm winds and moist air are conducive to fog formation, particularly in the cooler months when warm air meets cooler waters.

Snow can also significantly reduce visibility, especially during blizzards, but it often occurs seasonally and may not be as persistent as fog. Similarly, while thunderstorms can lead to poor visibility due to heavy rain, their occurrence is less frequent than fog. Dust or sand in the air can obscure vision, but this is generally linked to specific environmental conditions and doesn't occur as often or as broadly as fog. Therefore, fog is recognized as a common and persistent visibility issue in the region.