A rare blue moon will light up the sky tonight for the first time on Halloween in 19 years.

The term ‘blue moon’ is not related to the colour - it instead refers to when a second full moon appears in either a month or a season. The first full moon was on October 1.

A blue moon usually occurs every two or three years.

However, it is rare that a blue moon is happening on Halloween. It has been 19 years since this last happened and it will not happen again until 2039.

This year, the moon will rise at 4.53pm on October 31 and it is said that it will be in the sky next to a bright red object - Mars.