Footage of a lunar halo appearing in the skies over Donegal, Ireland early on Wednesday morning.

The video, filmed between midnight and 1am, shows the the halo appearing in the hazy sky, as a storm approached in the distance.

Halos of this kind occur when ice crystals in clouds interact with light.

On Wednesday morning between 12:00am and 1:00am while I was out sky watching I had a feeling there would be a good chance of a 22° lunar halo as conditions where with a hazy cloud in the sky with a weather front approaching from the west and then once it was dark enough the halo showed up not to strong at first but it then got strong for around a hour before heavier and thicker cloud moved in as the band of rain approached.
There’s an old weather saying: ring around the moon means rain soon. There’s truth to this saying, because high cirrus clouds often come before a storm. Notice in this photo that the sky looks fairly clear. After all, you can see the moon. And yet halos are a sign of high thin cirrus clouds drifting 20,000 feet or more above our heads.

These clouds contain millions of tiny ice crystals. The halos you see are caused by both refraction, or splitting of light, and also by reflection, or glints of light from these ice crystals. The crystals have to be oriented and positioned just so with respect to your eye, in order for the halo to appear.

That’s why, like rainbows, halos around the sun – or moon – are personal. Everyone sees their own particular halo, made by their own particular ice crystals, which are different from the ice crystals making the halo of the person standing next to you.