May Blue Moon 2026 UK: Where, When, And How To See It

May’s “Flower Moon”, or the full moon which marked the beginning of the month, has come and gone. But its second “blue moon” is yet to come.

In a relatively uncommon cosmic event, May 2026 will be bookended by a second moon – a “monthly blue moon,” to be precise.

Here’s what that means and when to see it.

There are two types of blue moons: seasonal and monthly.

The one we’ll see this May is a monthly moon. These are a little easier to understand than seasonal blue moons and, BBC Sky At Night Magazine explained, technically “astronomically incorrect”.

A monthly blue moon just means you see two full moons in the same month. That happens because while the moon takes 29.5 days to complete all of its phases, most Earth months have 30 or 31 days.

So, while our years have 365 days (except for leap years), 12 cycles of the moon take about 354 days. That’s a pretty big discrepancy.

As a result, every two to three years, we experience a 13th moon in the calendar year rather than a single full moon every month. This is called a “blue” moon, because unlike our regular moons, which are all called things like the “flower”, “blood”, and “wolf” moons, they aren’t named.

But this is a fairly new idea, first invented in 1946. They came about because of James Hugh Pruett, who misunderstood some dates in a farmer’s almanack.

The much older, original “blue moon” type is a seasonal blue moon, though the newer term is arguably the more common definition now.

Instead of looking at moons in an Earth month, seasonal blue moons relate to the astronomical season, which is marked by solstices and equinoxes.

The period between a solstice and an equinox is one astronomical season.

Most of the time, these only get three moons, but sometimes, because (like the Earth) the moon cycles aren’t perfectly aligned with these seasons, we get four.

A seasonal blue moon is the third moon in an astronomical season of four moons.

The next monthly blue moon, like the kind we’ll have on Sunday, will be on December 31, 2028.

But the next seasonal blue moon will fall on 20 May 2027.

May’s blue moon will rise on Sunday, 31 May.

Moonrise is set for 10:05pm that day.

But it’s technically expected to reach its peak on Sunday, 31 May at 9:45am, Royal Museums Greenwich said.

The moon will look full in the couple of nights before and after this, though.

It should be easy to see by looking up at the sky at night, though clear skies make this easier.

May’s blue moon is a “micromoon”, meaning it appears smaller and less bright than usual.