Rain and thunderstorms for the north, ‘polar outbreak’ set to hit the south

A polar blast is expected to hit the South Island with many areas already suffering as unseasonably low temperatures over the weekend.

The South Island towns of Picton and Culverden recorded the lowest temperature across the country on Saturday with both reaching a high of only 9c – well below the usual 17c for this time of year.

MetService meteorologist Sonja Farmer said the east coast of the South Island could feel the brunt of the cold snap in the coming days.

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“There will be some cooler temperatures… Sunday we’re expecting a cool max of 11C for Blenheim, and it’s a similar story for Sunday for Kaikōura, Asburton and Timaru. They can expect fairly low max temperatures tomorrow compared to what they normally get this time of year.

“Later in the week, overnight temperatures are going to get pretty low where we’ve got a cold snap coming through. This is the polar outbreak we’ve got coming. We know there’s going to be some cold temperatures,” she said.

Farmer said while the South Island was experiencing colder than usual temperatures, warmer weather and heavy rain were causing thunderstorms in the upper North Island. She said the North Island and top of the south can expect widespread rain over the coming days as a system of low pressure that dumped heavy rain over Northland slowly moves southwards.

While widespread rain was expected for much of the North Island and the Nelson and Marlborough regions, Farmer said the front was losing its intensity and there were no weather warnings in place.

“For the north of the North Island it’s (the rain) easing considerably. Things are starting to wane in terms of the amount and intensity of the rain, but the lower pressure system that’s affecting us at the moment has a few frontal features with it – it’s like an octopus with many tentacles,” she said.

The Bay of Plenty has suffered from heavy rain, with Ōpōtiki residents being urged to avoid “unnecessary” toilet flushing as wastewater pump stations were inundated with stormwater.

Farmer said the low fronts were slow moving and could still dump large amounts of rain as high pressure ridges were surrounding and containing the weather systems.

“On Sunday we’ve got showers again for Northland and Auckland and rain elsewhere across the North Island, and we’ve got thunderstorms possible from afternoon for inland areas north of Manawatū.

“It’s all to do with this system moving down over central New Zealand. The trough that has been affecting the upper North Island will move down to more central regions on Sunday and as that low spreads its fronts out over the North Island, the rest of the lower North Island and the far north of the South Island,” she said.

Farmer said while there were expected to be periods of rain for Marlborough, Nelson and the Buller regions, the rest of Te Waipounamu should stay dry.

”The South Island still has the influence of a slow moving ridge of high pressure, so it shouldn’t be too bad over there. There will be showers for the east and far north that will ease, and it will be predominantly fine for the rest of the island,” she said.

“For Monday the trough of low pressure will still have an effect on the North Island and there will be showers for most of the island with some possibly heavy falls. Ridges surrounding the low system to the east and the west of New Zealand and over the South Island is why the low is not moving very much,” she said.