A “super blue moon” is very rare: on average, it happens about once every 10 years, but the gap can range from a few years up to roughly 20 years.

What a Super Blue Moon Is

  • Blue moon : A blue moon is when there are two full moons in a single calendar month, or (by a second definition) when there is a third full moon in a season that has four full moons.
  • Supermoon : A supermoon is a full moon that occurs when the Moon is near its closest point to Earth in its orbit (perigee), so it looks slightly larger and brighter than usual.
  • Super blue moon : This happens only when those two things coincide —a blue moon that is also a supermoon.

Because it requires both a specific calendar timing and the right point in the Moon’s orbit, it is much rarer than either a blue moon or a supermoon alone.

How Often It Happens

Astronomers and NASA note that:

  • Supermoons: occur several times a year (about 3–4 full moons per year are supermoons).
  • Blue moons (of either type): occur about once every 2–3 years.
  • Super blue moons:
    • The average time between super blue moons is about 10 years.
* The gap can sometimes stretch to **around 20 years** between one super blue moon and the next.

A recent example was the super blue moon of August 2023 , and the next pair of super blue moons is expected in January and March 2037 , illustrating that they can sometimes cluster and sometimes be widely spaced.

Why It Feels So “Once in a Blue Moon”

Even though “once in a blue moon” has become a saying for something almost never happening, the actual pattern is more like “once a decade or so” for a super blue moon.

From a skywatcher’s point of view, that means:

  1. You might see a few of them in your lifetime.
  2. You can go many years without one, then suddenly get two in close succession (as expected in 2037).

If you spot one, it’s worth stepping outside for a look—these events combine the brightness of a supermoon with the rarity of a blue moon, making them a standout moment in the night sky.

TL;DR: A super blue moon happens when a blue moon and a supermoon line up on the same night, and this tends to occur about once every 10 years on average, though the gap can be anywhere from a few years to about 20 years.

Information gathered from public forums or data available on the internet and portrayed here.