The recent foggy weather has provided an opportunity to see the cousin of a rainbow: the fogbow. Although most common on mountains or in cold sea mists, they can be seen anywhere there is thin fog and fairly bright sunshine. If you’d like to find a fogbow, 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 point directly opposite the sun. Best chances are when the sun is still low on the horizon, less than 40 degrees. Fogbows are huge, almost the size of a rainbow but much broader. Some fogbows are very faint, so look for small bright spots in the misty background. Once caught, they are unmistakable.
Mary Knapp, Weather Data Library