The most common type is called radiation fog. It forms at night when the local air mass is stable, the skies are clear (resulting in rapid loss of heat from the land), and the layer of air above is at a higher temperature. When this confluence of conditions occurs, the morning’s winds become relevant. If the breeze is dead calm, the fog will rise to only 2 to 4 feet above the sea surface, presenting little challenge to navigation. But as the winds increase to a mere 5 knots, mixing the layers of air, fog can rise up hundreds of feet to obscure the waters ahead and obstruct reference points on land. This water-laden blanket is heavier than the surrounding air and tends to drain out of low-lying basins, valleys and river mouths; thus, with knowledge of local topography, one might accurately predict areas of exacerbated trouble. One fortunate characteristic of this type of fog is that it tends to “burn off” as the sun rises. But if one plans to wait out the fog, it must be noted that the farther from land one ventures, the slower the burn off.