A picture of a supermoon taken from Papamoa, Bay of Plenty.

The brightest supermoon in 68 years is set to cause king tides throughout the country when it lights up the sky this week.

However, it's not the larger-than-usual tides that are of any concern: rather, the winds of up to 140kmh that are expected to blast through central regions.

"Supermoons" occur when a full moon lines up with the sun, coinciding with the point in the moon's elliptical orbit when it is closest to Earth.

ANDY JACKSON A king tide in New Plymouth which saw a normal high tide rise by more than 1.5 metres.

The effect is a greater gravitational pull on the ocean, which results in "king tides" - the highest tides of a given year.

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These usually occur between four and six times a year.

EAMON PARKES The most recent supermoon seen from Richmond, Nelson.

According to a Metservice meteorologist Tom Adams, however, they are not forecasting any exceptional tidal events.

The difference between a regular full moon tide and king tide is negligible, he said.

"There'll be a small effect on tide, but winds reaching 140kmh is more important."

The winds are expected to reach gale-force in exposed areas throughout the Wellington, Wairarapa and Marlborough regions.

The top of the South Island can also expect severe weather, with heavy rain forecast for Nelson and Buller.

Adams stressed the two events are "completely coincidental".

"The moon isn't affecting the weather."

A spokesman for Civil Defence said the organisation was aware of the king tides, but was not aware of any advice or warnings related to them.

Auckland King Tides Initiative highlight on their website the importance of being careful while observing these super tides.

"Water levels during these King Tide events will be higher than normal, so take extra precautions when walking along the coast, particularly if bad weather is also forecast."

Surface flooding is also expected to occur in coastal Christchurch.