Thunderstorms bringing a threat of small tornadoes are forecast to rattle the top of the North Island this evening as central regions brace for powerful 140 km/h gales and heavy rain. 

Severe gales are set to sweep across parts of the country, as rain keeps falling at the top of the South Island and warning-level swells loom for the bottom of the North Island. 

Eighteen wind, rain and swell watches and warnings are in place as a slow-moving front lies over the northwest of the South Island, with a rapidly deepening low inbound from the Tasman Sea this morning, MetService said. 

The low is expected to cross the South Island between this afternoon and tomorrow morning, with connected fronts sweeping across the North Island. 

Nelson City Council said the area is already being impacted by the wild weather, with power outages and flooded roads being reported. 

The council said there is surface flooding between Nelson and Renwick. 

Network Tasman said a fallen tree has taken out powerlines that feed a section of Wakapuaka Rd, Cable Bay, Teal Valley and Kokoroa, leaving the area without power. 

MetService warns winds could gust up to 100km/h, along with small tornadoes. Photo / MetService 

Electrical storms are currently brewing in the Tasman Sea with western parts of the country, including Auckland, in the firing line later today. MetService warns winds could gust up to 100 km/h along with small tornadoes. 

Meanwhile, the Tasman District, Buller and Grey districts, Nelson Lakes National Park and the ranges of Nelson and Marlborough, between Nelson city and the Awatere River, lie under heavy rain warnings until this evening, with thunderstorms possible. The highest rain totals are expected in Tasman District where up to 300mm could fall in the ranges. 

“Surface flooding, slips, and difficult driving conditions possible,” MetService said for all those under rain warnings. 

Severe gales gusting up to 130km/h have also sparked wind warnings for Wellington until early tomorrow morning, and from 1pm to 10pm today in Taranaki. 

Marlborough southeast of the Awatere River and the Canterbury high country were also under a warning for severe gales, which could reach 140km/h in Marlborough and Canterbury north of the Rangitata River, and 120km/h elsewhere in the region’s high country. 

“Damage to trees, powerlines and unsecured structures possible.” 

A heavy swell warning has been issued for Kāpiti-Porirua Coast – Kāpiti Island to Cape Terawhiti from 9pm to 7am tomorrow, with northwest combined waves rising to 4 to 4.5m. 

Heavy rain watches are also in place for Taranaki Maunga, the Southland mainland and the headwaters of Otago lakes and rivers, with strong wind watches for Taihape, inland Whanganui and the top and west of the South Island from this afternoon. 

Strong wind watches have been issued for Christchurch and Canterbury Plains north of the Rakaia River, as well as Wairarapa and Tararua District, from this evening. 

Amid the gloom, one district should enjoy a short respite this morning, MetService meteorologist Katie Lyons said. 

“Westland will still be in this lull between the systems, but north of Westland it’s just one continuous event.” 

Despite a break in the rain, the district’s ranges were still expected to receive up to 600mm of rain since the wet weather began, Lyons said. 

“If anywhere in the country were ready to take it, it’s Westland, but it’s still a huge amount. Further north, we’re looking at up to about 350 millimetres of rain for the Buller … Tasman, Nelson/Richmond ranges area.” 

And while the first of the two lows walloping central and southern parts was a rain event, the second would bring wind. 

“[The] strong wind warnings for the Canterbury high country … Marlborough, southeast of the Awatere Range, that’s just as these really strong northwesterlies go up and accelerate down the other side of the ranges." 

A cold change is on the way after this week's wet and windy weather, which could be good news ahead of the ski season. Photo / Mt Hutt/Cardrona Alpine Resort 

However, the heavy rain and strong winds would be short-lived, she said. 

“It’ll be getting wetter into [today], maybe a bit wet [tomorrow], and then back to sort of stock standard showers.” 

But it won’t be shorts and jandals weather – a cold southwesterly change could mean snow for some. 

“Temperatures will drop and we’ll be starting to talk about snow to some low levels for the South Island, down to about maybe 500m. That’ll affect [alpine] passes throughout there as well. 

“So it’ll be a completely different story towards the end of the weekend.”