How do double rainbows form?

On Thursday morning, a double rainbow was spotted over San Diego, California, after a cold front brought scattered showers to southern California.

A rainbow may be on the horizon when you see a spring shower on the WeatherRadar. When sunlight enters a water droplet, it causes the light to bend (refraction) and separate into its component colors as it passes through the droplet. The light then reflects off the back of the droplet, and then refracts again as it exits, creating the visible spectrum of colors we see as a rainbow.

Sometimes more than one rainbow is visible. Double rainbows occur when sunlight is reflected twice within a raindrop, with the violet light that reaches the observer's eye coming from the higher raindrops and the red light from lower raindrops.

This means the colors are inverted compared to the primary rainbow, with the secondary rainbow about 10 degrees above the primary bow.