Residents across Catalonia will be able to see a Blue Moon on 31 May, a rare lunar event that happens roughly every two and a half years. This month’s full moon will also be a micromoon, because the Moon will be at its furthest point from Earth in its orbit.
Despite the name, a Blue Moon does not mean the Moon will look blue. The term, used in the Anglo-Saxon world, refers to the second full moon in the same calendar month, according to Betevé.
The Moon’s cycle lasts about 29.5 days, which does not line up neatly with the 365.24-day calendar year divided into 12 months. That is why some years have 12 full moons and others, such as 2026, have 13. When there are 13 full moons in a year, one month will have two full moons, and the second one is called a Blue Moon.
The previous Blue Moon was on 31 August 2023. After this month’s event, the next one will not be until 31 December 2028, which falls on New Year’s Eve. Later Blue Moons are scheduled for 30 September 2031, 31 July 2034 and 31 January 2037. The 2037 Blue Moon will also be a supermoon, as was the case in 2023.
This May’s Blue Moon will be a micromoon, which means it will be the smallest full moon of the year. That happens when the Moon reaches apogee, its furthest point from Earth. On 31 May, the Moon will be nearly 406,000 kilometres away. For more Catalonia-wide news, see our news page.
By contrast, a supermoon happens when the Moon is at perigee, its closest point to Earth. Catalonia will have two supermoons in 2026, in November and December. The next time a supermoon and a Blue Moon coincide will be in January 2037. The last time a micromoon and a Blue Moon happened together was on 31 October 2020.