Fog Bow

weather · light · rainbows · fog

White rainbow in fog. A fog bow looks like a rainbow but appears in fog instead of rain. It's sometimes called a white rainbow because it's so pale and ghostly compared to a regular rainbow.

Tiny water droplets. Fog bows happen because fog has water droplets smaller than 0.05 millimeters, which is way tinier than rain droplets. These super small droplets make the colors much weaker and harder to see.

Barely there colors. When a fog bow does have colors, you might spot a red outer edge and a bluish inner edge, but they're so faint they look almost white. The tiny droplets spread out the light in a way that smears the colors away.

Diffraction effect. Light bends and spreads out differently when it hits very small water droplets, and this is called diffraction. That spreading effect is what makes fog bow colors fade away instead of being bright and clear like in a regular rainbow.