A runner spotted a “fire rainbow” over Pinnacles National Park in California, the National Weather Service, Bay Area announced on Wednesday.
A fire rainbow, more formally known as a circumhorizontal arc, occurs when the sun is more than 58 degrees above the horizon. The sun must be higher than this in order for the arc to form, according to Atmospheric Optics.
Then, as the sun’s light is refracted off of the ice crystals in cirrus clouds, “you get pretty colors,” Roger Gass, a meteorologist with the National Weather Service (NWS), told SFGate.
"It's an optical illusion,” he added.
If you live in North America, you have a good chance of seeing the phenomena, especially during the summer months. In fact, depending on where you live in the states, a fire rainbow can be spotted five or more times during the summer, according to Atmospheric Optics.
Fire rainbows are extremely uncommon in Northern Europe, however, and are “impossible to see north of Copenhagen,” the weather site says.