August is a big month for the Moon. Not only are there two full moons this month – making the second a blue moon – but both are also supermoons.

And, by some reckoning, they are the middle two of a sequence of four supermoons – with the August supermoons being the closest to Earth of the four.

The first super full moon of August was essentially overnight Tuesday continuing into Wednesday night. The actual moment of full moon is at 6.32am Wednesday, according to the Royal Astronomical Society of NZ.

At this time of year that’s before dawn, with sunrise in Bluff on Wednesday at 8.07am, while in Kaitaia – at the other end of the country – it will be at 7.21am.

Moonset will be at 7.48am in Kaitaia and 8.45am in Bluff.

The exact moment at the end of August when the super blue moon is full will be at 1.36pm on August 31.

Essentially a supermoon happens when the Moon’s orbit is closest – or at perigee – to Earth about the time of a full moon.

Supermoon is not a technical term, and by some definitions, only the two August full moons in the sequence of four are considered supermoons.

New moons at perigee – the other time when the Sun, Earth and Moon are in a line – are also classed as supermoons, but for obvious reasons attract little general attention.

According to Nasa, high tides and low tides will be more extreme with a perigean full moon, and more so for an extreme perigean full moon.

“The extremes are greater due to the difference in the gravitational pull of the Moon across Earth’s diameter,” Nasa says.

Periods with the highest tides have a potential for increased coastal inundation, depending on weather conditions.

Niwa calls these “storm-tide red-alert days”, with August 1-6 and August 30 to September 4 being in that category.

EarthSky puts the distance between Moon and Earth at 357,530km on Wednesday, and a slightly closer 357,344km at the end of August.

There won’t be a closer supermoon until November 2025, when the distance will just sneak under 357,000km.

The Moon will appear more impressive near the horizon, that’s just a trick of your brain.

“Photographs prove that the Moon is the same width near the horizon as when it's high in the sky, but that's not what we perceive with our eyes,” Nasa says.

“Thus it's an illusion rooted in the way our brains process visual information. Even though we've been observing it for thousands of years, there's still not a satisfying scientific explanation for exactly why we see it.”

-Michael Daly/Stuff.