City residents in Alor Setar were left with a visual treat of a rainbow-like ring circling the sun or moon, known as the halo phenomenon, which was detected since yesterday afternoon.

According to a statement from the Meteorological Department, the occurrence was a natural phenomenon.

“There are many kinds of halos, but most of them are caused by ice crystals in the high cirrostratus clouds which are wispy layers of clouds situated at between 6,000 to 18,000 metres above the ground,” it said.

It said in forecasting weather, halos can be used to indicate rain or thunderstorms within a 12 to 24-hour period, especially if they are followed by mid-level clouds.

The statement said the cirrostratus cloud layer was so thin that the sun or moon can be viewed clearly through it, but could also sometimes be seen as dull shadows through heavier cloud layers.

When light from the sun or moon shines through ice crystals in cirrus clouds, the light refracts and creates a halo.

The statement added that members of the public who wish to view the halo must ensure that their eyes are protected from the sunlight.

“Never attempt to look at a halo directly or during a long period of time, and it is wise to shield their view from behind construction, buildings or anything else,” it said.

It is also advised to practice caution when photographing halos without sun protection because it may be dangerous, especially when using single-lens reflex (SLR) cameras.

- Bernama