SINGAPORE - Many in eastern Singapore who looked skywards at close to noon on Tuesday (Sept 22) were treated to the sight of a large halo that ringed the sun.

The sun halo was spotted at locations such as Tampines, Simei and Ubi at around 12.05pm. Photos of the brilliant, multi-hued halo quickly made their way across messaging groups.

The optical phenomenon, which is not uncommon, typically occurs when there are thin clouds so high in the sky that they are made of ice crystals rather than water droplets.

The crystals act as tiny prisms, reflecting and refracting light in such a way that a ring is seen around the sun.

Readers of The Straits Times have asked if it is possible to forecast when something like this would happen. A less distinct halo was seen about three weeks ago, near the Merlion.

The National Environment Agency said previously that it is difficult to forecast the precise location of these ice crystals in the atmosphere, which would determine where the halo can be sighted.

It also said that while it is safe to look at the halo itself with the naked eye, it is dangerous to look at the sun directly without proper protection.