A beautiful fire rainbow formed over the sky in Bangkok, Thailand, on June 2.

The weather phenomenon, known as cloud iridescence or irisation, formed shortly before sunset at around 6pm.

Amazed residents recorded the colourful sight on their phones.

Dr. Matichon Tangmatmattham, from the country's National Institute of Astronomy said the formation was a ''iridescent pileus cloud'', which he nicknamed a ''rainbow hat cloud''.

He said: ''In this case it occurred when the cumulonimbus clouds rise in vertical air flows. The air layer with the humidity is lifted and condenses into water droplets so the cloud appears to 'wear' a rainbow hat when sunlight shines through the droplets.''

Rainbow clouds are formed when sudden condensation in rising clouds forms small water droplets or ice crystals.

These then reflect the bright sunlight to create a multi-coloured rainbow effect, like the prisms of light seen in soap bubbles or oil on the surface of water.

A beautiful fire rainbow formed over the sky in Bangkok, Thailand, on June 2.

The weather phenomenon, known as cloud iridescence or irisation, formed shortly before sunset at around 6pm.

Amazed residents recorded the colourful sight on their phones.

Dr. Matichon Tangmatmattham, from the country's National Institute of Astronomy said the formation was a ''iridescent pileus cloud'', which he nicknamed a ''rainbow hat cloud''.

He said: ''In this case it occurred when the cumulonimbus clouds rise in vertical air flows. The air layer with the humidity is lifted and condenses into water droplets so the cloud appears to 'wear' a rainbow hat when sunlight shines through the droplets.''

Rainbow clouds are formed when sudden condensation in rising clouds forms small water droplets or ice crystals.

These then reflect the bright sunlight to create a multi-coloured rainbow effect, like the prisms of light seen in soap bubbles or oil on the surface of water.