Blue moon to appear at Halloween for first time in 76 years

October 31 will be a blue moon, meaning it is the second full moon to occur in the same month

A 'supermoon' pictured over Dubai in April 2020. Antonie Robertson / The National

The full super moon rises over Sheikh Zayed Grand Mosque in Abu Dhabi in November 2016. The moon is the closest its been to Earth since 1948. Christopher Pike / The National

A 'supermoon' rises over Dubai Sports City in June 2013. Pawan Singh / The National

The super moon rises over Media City in Dubai in August 2014. Antonie Robertson / The National

Photography enthusiasts take pictures of the moon on the Palm Jumeirah Dubai in June 2013. Lee Hoagland / The National

The 'supermoon' rises over the Sheikh Zayed Mosque in Abu Dhabi in June 2013. Antonie Robertson / The National

A 'supermoon' pictured from Al Thuraya Astronomy Centre in Mushrif Park in Dubai in January 2018. Pawan Singh / The National

A 'supermoon' pictured over Dubai in April 2020. Antonie Robertson / The National

It is said weird things happen when it is a full moon and Saturday’s one is right on time – falling on Halloween night.

But this one is extra special.

Not only is it a full moon tonight, it is a blue moon and a particularly rare one at that.

The National explains what a blue moon is and why it is special.

What is a blue moon?

Normally there is only one full moon a month. A blue moon is the second full moon to be seen in the same month.

The first full moon of October happened on October 1-2. This one occurs on the night of October 31.

Why is this moon even more special?

Because it coincides with Halloween, and full moons on October 31 do not happen often.

The last time it happened was almost 20 years ago, in 2001. And it will not occur again for another 19 years.

But the extra special thing about this full moon is it can be seen across all time zones in the world – something that has not happened since 1944, and will not happen again until 2039.

It will, however, look a little bit smaller than usual, as it is further from the Earth, making it a micro moon, which is the opposite of a super moon, that is around 14 per cent larger and 30 per cent brighter in comparison.

Is the moon actually blue? 

No the moon will not actually be a blue colour.

It is an expression to describe an event that is not exactly rare, but not common either – exactly like a blue moon, which happen every two and a half years or so.

However, the moon can on occasion appear blue when there is dust or smoke high in the Earth’s atmosphere.

That happened almost every night in the late 1800s, when Krakatoa, a volcano, exploded in Indonesia.

According to Nasa, some of the ash-clouds were filled with particles about one millionth of a meter wide, changing the colour of moonbeams shining through the clouds that emerged as blue, and sometimes green.

Blue coloured moons – and lavender suns – persisted for years after the eruption due to the phenomenon, said the space agency.

Sometimes the sunsets were so vivid fire engines were erroneously called out in the US to fight phantom fires.