Blood moons - also known as total lunar eclipses - occur when the Earth lines up between the Moon and the Sun.
This hides the Moon from sunlight and blocks most of the blue light, with the remaining light refracting onto the Moon's surface and causing a red glow.
A "supermoon", meanwhile, occurs when the Moon is at its closest point in its orbit around Earth - making it appear much larger than usual.
The lunar eclipse is due to last five hours, beginning at 8.47pm next Wednesday, and ending at about 1.49am the next morning.
However, the period of "totality", where the Moon is completely hidden from the Sun by Earth, and when the reddening is most noticeable, will only last about 14 minutes, from 11.11pm - making it one of the shortest eclipse totality periods.
"Blood supermoons occur every few years, but aren't always visible in Aotearoa, with the last one in December 1982," Stardome Observatory and Planetarium astronomy educator John Rowe said.
"We've waited almost 40 years for this, so it's exciting."
MetService meteorologist Tui McInnes said a low-pressure system sitting to the northeast of Aotearoa would bring southeasterly winds across most of the country - causing quite cloudy conditions, particularly for the east coast of the North Island (Te Ika-a-Māui).
That meant areas such as Hawke's Bay, Wairarapa, Gisborne, Bay of Plenty, Coromandel, Auckland and Northland were less likely to have an unencumbered view of the rare lunar phenomenon thanks to the expected overcast conditions.
McInnes said it was difficult to predict what conditions might be for Taranaki and elsewhere on the west coast, but he anticipated the skies may be clearer than on the east coast.
It was a different story for people in Te Waipounamu (the South Island), especially for those in Central Otago and the Canterbury High Country, who should be in a great position to see the blood supermoon.
Similar to the North Island, predicting conditions on Te Waipounamu's west coast was not as straightforward. McInnes said the sooner winds shifted to a northerly/northeasterly direction, the more likely cloud would develop with the Southern Alps acting as a moisture trap.
Stardome researcher Dr Grant Christie, who has been associated with the observatory since 1967, said he expected a few amateur astronomers could travel to the South Island to give themselves the best chance of seeing the blood supermoon.
"You do have those very dedicated enthusiasts ... they will travel all over the world to watch eclipses."
Christie anticipated the red hue shown on the Moon on Wednesday may not be as deep as in past events, given its expected trajectory. He explained that the Moon would only narrowly pass through the central part of the shadow, known as the umbra, cast by the Earth onto the moon.
In the United States, the lunar event is also called a "flower" moon or "pink" moon - nicknames given by farming and indigenous communities due to certain flowers blooming in May.
