Weather phenomenon known as ‘fire rainbow’ spotted in Hong Kong skies

Observatory shares video, explaining ‘circumhorizontal arc’ is not true rainbow but optical phenomenon formed by sunlight refracting through clouds

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.”