When there’s fog in the Valley, the boundary where sun and fog meet often creates interesting tricks of light, like this fogbow seen up in the hills on Thursday morning.
Fogbows are formed by the same light-scattering process as rainbows. But fog is made up of much smaller water droplets than rain, causing it to diffract light differently. The result is bows that appear mostly white, with little or no color.
The website Atmospheric Optics gives the following guidance for finding fogbows:
Search when the sun breaks through mist or fog. Look away from the sun and at an angle of 35-40° from your shadow which marks the direction of the antisolar point. Some fogbows have very low contrast so look for small brightenings in the misty background. Once caught, they are unmistakable.