Wispy spiralling clouds painted in hues of orange, yellow, green and blue hovered in the skies above Hong Kong last week, a rare sight that only occurs when the sun is at a high angle.

The Hong Kong Observatory shared the video of the “fire rainbow” on Monday, a meteorological phenomenon so named because it looks like a rainbow burning in the sky.

“However, it’s not a true rainbow but rather an optical phenomenon called a circumhorizontal arc,” the forecaster explained in a social media post.

“It forms when sunlight refracts through hexagonal, plate-shaped ice crystals within cirrus clouds.”

The formation of a circumhorizontal arc is highly dependent on the sun’s angle of incidence, it added, and only has a chance of appearing when the sun is near midday.

The video was taken by a social media user, Star Fish, and was shared on the Community Weather Observing Scheme page on Facebook.