As the saying suggests, a blue moon is a rare event. This weekend's Full Flower Blue Moon is even rarer still, happening only every dozen or so blue moons.
But despite what its name suggests, this full moon will not actually by blue. The name simply refers to the fact that it is the fourth full moon of the season, when typically there are only three full moons in a season.
In 2019 there has already been a Blood Moon, a Pink Moon and a Super Worm Moon – each named after various occurrences that take place at the time of year the full moon appears.
The Flower Moon, which is set to rise at dusk on Saturday 18 May, is appropriately named after the the flowers that bloom in the month of May.