Full Blue Moon over Cape Town coming, but is it really blue?

Skywatchers across South Africa will be treated to a Blue Moon on Sunday, 31st May. Is it going to be a blue colour? The answer depends on what type of “Blue Moon” it is.

A Blue Moon is (usually) not blue in colour at all. Instead its about its rarity and timing. So “Blue” is the name given to a full moon event that happens because the Moon’s cycle does not fit perfectly into our calendar.  A calendar Blue Moon is the second full moon in a single calendar month. So May 2026 is going to have two full moons – it had one on the 1st May (the Flower Full Moon) and now the second one, coming on the 31st May (the Blue Moon). 

Time Out Tip: Moonrise begins at 5:40 PM to 5:50 PM South African time (SAST), close to sunset. 

To make it even more weird, there is also such a thing as a ‘seasonal Blue Moon’. This refers to the third full moon in a season that contains four full moons instead of the usual three.  A “season,” in this context, is the period of time between a solstice and an equinox. Each season typically lasts three months and typically has three full moons. If the season has four full moons, then third one is called a ‘seasonal Blue Moon’. Which explains how the expression, “once in a blue moon” came about – it’s clearly an uncommon event! 

When is the moon really blue?

Sometimes, however, the moon can appear blue in colour but this only occurs after major volcanic eruptions or large wildfires. The moon takes on a bluish tint because tiny smoke or dust particles in the atmosphere scatter red light. 

Is it going to be a “big” moon?

The Blue Full Moon on the 31st May is actually the most distant full micromoon of 2026.

What’s a ‘micromoon’? That’s when the new or full moon is at its greatest distance from Earth.  So it will look about 7% smaller than an average full moon.

Don’t worry – the moon will always look big when it rises above the horizon. Ever wondered why? Well, Nasa says that it isn’t some trick of the light or atmospheric physics. It’s actually an optical illusion. They are unclear exactly why it looks bigger but clearly we know the moon's physical size doesn't change. Instead, your brain is tricked by context. When the moon is low on the horizon, your brain compares it to foreground objects like trees and buildings, making it appear massively magnified in comparison. That’s the theory anyway.  

Where to watch the Blue Moon rise: 

• Lion’s Head is one of the best places to watch the moonrise and the summit gives spectacular 360° views. There is something very romantic about watching a golden (Blue) moon rising above the twinkly lights of the city. If you’relucky there will even be some twinkly fireflies around! If you do climb up to Lion’s Head, start before sunset, bring a head torch, and avoid hiking entirely alone late at night. Note that this trail includes ladders, so if this is not the best option for you, try a beach blue-moon viewing instead.

• Any of the Cape Town beaches that have a clear eastern horizon, and with minimal mountain obstruction, are good for watching the moon rise over the sea. Boulders Beach and Fish Hoek beach are also good viewpoints, and you might even see some twinkly bioluminescence in the moonlit waves. The Shark Spotters Lookout Point / Observation Deck on Boyes Drive is also an excellent elevated point at which to watch the moon rise across False Bay. 

How to make the most of the full moon:

• Arrive 30–45 minutes before moonrise, to settle in for the show (and to let the wine breathe)
• The moon often looks largest and most golden just above the horizon. 
• Bring warm layers — late May evenings can be cold and windy 

Did you know? The silver path of moonlight across the ocean is often called a moon glade — a luminous trail that appears to shimmer on the water between the viewer and the moon.