Weather: NZ set to be 'swiped' by huge incoming storm

Summer is officially here. Before you slip on your jandals and head to the beach though, be warned - a big storm is on the way.

A huge area of low pressure is forming in the Southern Ocean, with the resulting storm set to span thousands of kilometres in diameter.

Although the storm won't directly cross New Zealand, "it's so large in size it can't help but swipe us" according to WeatherWatch. 

The storm will impact our weather for the next week, bringing pockets of severe weather to both islands.

It's not all doom and gloom though.

"For some areas it may enhance the sunny and hot weather you've already been having lately," predicts WeatherWatch.

Those areas least affected by the storm are the north of the North Island, the eastern North Island north of Masterton and Hawke's Bay.

NIWA meteorologist Chris Brandolino says December is going to be an "active" weather month, particularly in the South Island. 

Starting Monday, the south is set to get a good dose of wind and rain. The wettest areas will be west of the Southern Alps, he says, with Westland, Hokitika, Haast, and Franz Josef in the firing line for the worst of the rain.

"Hundreds of millimetres we're talking over the next 24 to 36 hours, with more to come as the week unfolds," Brandolino told The AM Show on Monday morning. 

"Even for their standards this is going to be a lot of rain and a lot of wind."

He says flooding around those regions is a "distinct possibility".

"That much rain in a short period of time [means] rivers will rise really quickly, so that's something we need to be mindful of."

On Tuesday, the strong winds will head north to Wellington, says Brandolino.

Map showing three-day rainfall totals until 7am Thursday.
Map showing three-day rainfall totals until 7am Thursday. Photo credit: WeatherWatch

Last week NIWA released its summer season forecast, with warmer-than-average temperatures expected for most of the country.

"We feel with pretty good confidence that temperatures will be above average for the three month period and that includes everyone except the West Coast," Brandolino told The AM Show. 

Rainfall for most of the country was forecast to be "near normal", with the exception being the west of the South Island, where above-normal summer rainfall is a possibility.

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