Another sub-tropical storm looms large off the eastern coast of the North Island.

Niwa says the large storm is expected to develop and swirl to the northeast of New Zealand this weekend and into next week.

Those on the East Coast are being told to brace for giant 4-metre waves.

But those still mopping up from last week's devastating Cyclone Cook can breathe a sigh of relief with this next tropical deluge not expected to bring anywhere near the same incredible levels of rain and powerful wind.

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MetService forecaster Cameron Coutts said at this stage it was a little bit too far out to get a really good handle on where the storm was going to track.

But the most likely model showed the tropical low moving south across the Pacific from Niue to lie close to the Kermadec Islands north-east of New Zealand.

"Our models show it moving off to the east of the North Island, and it certainly will generate some swell," said Coutts.

The entire eastern coastline from Northland down to Wairarapa would be affected by seas whipped up by the storm as it tracked south.

It was unlikely to bring destructive levels of wind and rain to storm-weary regions and no watches or warnings had been issued.

Weatherwatch.co.nz said the storm forming in the Pacific to the north was likely to track very close to East Cape.

Weather analyst Philip Duncan said it was good news for surfers as well as those impacted by recent cyclones with the storm expected to remain just offshore.

At worst it would bring a few showers and easterly winds as it brushed past the North Island.

But as the storm marched across the Pacific, the country was set to enjoy a fine autumn weekend with an enormous high anchored over central New Zealand straddling both islands.

Most regions could expect clear nights with temperatures dipping into chilly single figures with even a chance of frost in sheltered parts.

There was also a risk of fog and mist patches but this was expected to burn off quickly in thanks to the warm sunshine.