Mist and fog, any difference?

The answer lies in their thickness – and how far we can see through them (ie: the visibility). If we can see less than 1 km through the cloud of water droplets, it is known as fog. If we can see between 1 and 2 km, we call it mist.although mist and fog look like smoke, they are actually tiny drops of water floating in the air. In fact, they are clouds that have formed at ground level. Mist and fog usually form at night when the air is too cold to hold all its moisture. Clear skies mean that the ground gets cold and it then cools the air close to it. This cool air causes condensation and water droplets form in the air. Fogs are thickest when the air can hold a lot of moisture. Although mist is not as thick as fog, they are both formed in this same way. Mist, however, usually stays closer to the ground and you can see over the top of it. Mist is often seen on autumn mornings when nights get longer and cooler again. This is particularly true in valleys, because cold air sinks down and collects in the valley during the night. Mist and fog also form over areas where there is plenty of moisture, such as San Francisco fogriver valleys, lakes and harbours. If warm air meets cold seas or waters (or any cooler surface) then condensation will once again occur and fog will form. This explains the example of San Francisco, where the Golden Gate Bridge is often surrounded by mist and fog. This is formed as the warm California air from the south is chilled as it blows over the cold sea currents in the Pacific.